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 [Search a list of Patent Appplications for class 324]   CLASS 324,ELECTRICITY: MEASURING AND TESTING
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SECTION I - CLASS DEFINITION

This is the residual home for all subject matter, not elsewhere classified, relating to the measuring, testing (or sensing) of electric properties, (e.g., determining ground resistivity, determining frequency of an alternating current, determining kilowatt hour demand), or the measuring, testing or sensing of nonelectric properties by electric means (e.g., determining moisture, a nonelectric property, by measuring conductance with a resistance bridge; determining speed, a nonelectric property by use of an electric tachometer).

(1) Note. Measuring and testing have been distinguished as being quantitative and qualitative, respectively, but in these definitions the terms are used synonymously.
(2) Note. This class was produced in 1953 by making official the unofficial digests which had been established by the Examiners of Class 175 (Division 48) during the period from about 1905 to 1952, and, in the case of subclasses 76+, by cursorily revising the unofficial digests which had been established by the Examiners of Classes 171 and 172 (Division 69) during the period from about 1902 to 1952. A caveat is given: While it is believed that the titles and definitions are reasonably correct, no assurance can be given that all of the patents, issued prior to the date of reclassification, are in the proper subclass, since only some of the individual patents were read during the reclassification project. Consequently, in making a thorough search in this class, it is advisable to investigate every subclass which may possibly be pertinent and not, in order to shorten the search, to rely upon the principle of superiority of subclass subject matter because of position in schedule, since the principle is applicable only in classes where each patent has been analyzed and placed in the schedule in accordance with that portion of the disclosed subject matter which is claimed.
(3) Note. Measuring and testing requires sensing and signaling or indicating to exhibit the result of the sensing. Sensing is synonymous with condition responsive. Sensing merely detects the presence and/or magnitude of the condition.
(4) Note. Since many other classes include condition responsive subclasses, often entitled automatically responsive or automatic, the search for sensing, in order to be complete, must extend to the class which relates to the environment in which the sensing occurs. Some of these classes are listed below under SEARCH CLASS.
(5) Note. Since Class 324 takes, under the class definition, only measuring and testing not elsewhere classified, the search, in order to be complete, must in appropriate instances extend to the other classes listed below under SEARCH CLASS.
(6) Note. The combination of the subject matter of this class (324) and an art environment is generally classified with the art environment where that environment is significant, either by virtue of a significant disclosed relationship or by virtue of a claimed relationship, as where a test is made of the condition of a portion of a telephone system without making said portion of the telephone system unavailable for use. Where the art environment is recited by name only the combination may be classified, in some instances, with the art environment, and in others, in this class (324). For a list of some of the other classes which contain pertinent subject matter, see the classes referred to under SEARCH CLASS.

SECTION II - LINES WITH OTHER CLASSES AND WITHIN THIS CLASS

Class 324, subclasses 870.01+ take telemetric-signaling means useful in transmitting a measured quantity, not limited to any particular measuring instrument provided for in other classes, while Class 324 takes such telemetric-signaling means in combination with a particular measuring means of the type provided for in Class 324.

LINE BETWEEN CLASS 340 AND CLASS 324

See Class 340, Communications: Electrical, appropriate subclasses, for subject matter sometimes similar to that in Class 324. Often, but not invariably, the line between these two classes is as follows: If the testing system is permanently associated with the environment being tested, as in a machine monitoring device or in a burglar alarm, classification is in Class 340, while if it is temporarily associated, as in a portable test set, such as used by linemen, classification is in Class 324. Note particularly subclasses 870.01+ for telemetering and subclasses 500+ for signaling, automatically responsive to a condition.

LINE BETWEEN CLASS 429 AND CLASS 324

See Class 429, Chemistry: Electrical Current Producing Apparatus, Product and Process, subclasses 61+ for automatic battery control means combined with the battery, and subclasses 90+ for battery having measuring, testing, and indicating means. See Class 324, subclasses 20+ and Class 340, subclasses 636.1-636.21 for this subject matter.

SECTION III - REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:

29Metal Working,   subclass 25.35 for the electrical measuring, testing or sensing of piezoelectric crystals combined with the manufacture thereof, and subclass 25.41 for the electrical measuring, testing or sensing of condensers combined with the manufacture thereof.
33Geometrical Instruments,   subclasses 125+ , for the determination of distance, and subclasses 300+, for magnetic field direction sensing and indicating.
73Measuring and Testing,   appropriate subclasses for nonelectrical measuring and testing and for electrical measuring and testing of the following types: subclasses 26+ for gas analysis by electrical thermal determination,. subclass 75 for moisture determination by electrical thermal conductivity; subclass 760 for stress and strain gages, subclasses 104+ for surface and cutting edge determination by sliding pick-up, subclasses 112.01 - 112.06 for turbine engine testing, 114.01 - 114.81 for internal combustion engine measuring and testing, and especially 114.58 - 114.67 for electrical system testing of an internal combustion engine. Subclass 304 for liquid level gages; immersible electrode type; subclasses 305+ for float type, subclass 755 for fluid pressure (e.g., Pirani type), subclasses 488+ for speed.
100Presses,   subclass 99 for presses having electrical measuring, testing or sensing means.
156Adhesive Bonding and Miscellaneous Chemical Manufacture,   subclasses 47+ for methods of making or joining conductors of indefinite length.
178Telegraphy,   appropriate subclasses particularly subclass 69 , for telegraphy combined with electrical measuring, testing or sensing.
181Acoustics,   subclasses 101+ , for geophysical or subsurface exploration involving mechanically transmitting or receiving sound waves, subclasses 123+ for mechanical sound echo systems in general, and subclass 125 for mechanical sound location means.
204Chemistry: Electrical and Wave Energy,   subclass 400 , for the analytical and testing apparatus related to the subject matter of that class, and subclass 242 for electrolytic cells, per se, (e.g., Beckmann cell).
205Electrolysis: Processes, Compositions Used Therein, and Methods of Preparing the Compositions,   appropriate subclasses for electrolysis utilized for electrochemistry and especially subclasses 775+ as the residual home for a process of electrolytic analysis or testing, per se.
209Classifying, Separating, and Assorting Solids,   for the subject matter of that class even if the basis of the separation is an electrical determination. Note subclasses 127.1+ for electrostatic separation and subclasses 212 and 213+ for magnetic separators, subclasses 511, 524+, 536, and 576 for photoelectric assorting.
250Radiant Energy,   subclasses 200+ for miscellaneous photoelectric cell circuits, subclass 250 for wave meters for measuring the wavelength or frequency of radio and microwaves, subclass 281 for methods and apparatus for ionic separation or analysis, subclasses 302+ for fluorescent and radioactive tracer methods, subclasses 336.1+ for the detection of invisible radiation or the examination of material by invisible radiation using radiant energy responsive electric signalling means, subclasses 428+ for fluent material containing, support or transfer means with or without an irradiating source or radiating fluent material, subclasses 453.11+ for supports for objects of irradiation, subclasses 458.1+ for luminophor irradiation, subclasses 472.1+ for nonelectric invisible radiation detectors, subclasses 493.1+ for radiant energy generation and sources, subclasses 505.1+ for radiation controlling means and subclasses 522.1+ for source supports.
273Amusement Devices: Games,   appropriate subclasses for games (e.g., pin-ball machines, target range) having electrical indicators.
307Electrical Transmission or Interconnection Systems,   subclass 111 for systems which are nonresponsive to frequency change and subclass 152 for systems which are responsive to rate of change.
313Electric Lamp and Discharge Devices,   subclass 10 for the subject matter of that class with integral temperature indicators.
314Electric Lamp and Discharge Devices: Consumable Electrodes,   appropriate subclasses (note particularly subclass 9 ) for the subject matter of that class combined with measuring, testing or sensing.
315Electric Lamp and Discharge Devices: Systems,   appropriate subclasses (note particularly subclasses 129+ ) for the subject matter of that class combined with measuring, testing or sensing.
318Electricity: Motive Power Systems,   appropriate subclasses for automatically responsive motor systems and subclass 490 for motor systems having signals, meters, recorders or testing devices.
320Electricity: Battery and Condenser Charging and Discharging,   subclass 48 for battery charging and discharging systems having indicating, signaling and/or testing means.
322Electricity: Single Generator Systems,   subclasses 17+ for the subject matter of that class automatically responsive to a condition.
323Electricity: Power Supply or Regulation Systems,   subclasses 234 through 303for the subject matter of that class automatically responsive to a condition.
329Demodulators,   for amplitude frequency, phase or pulse demodulators which may include an indicator.
330Amplifiers,   appropriate subclasses, for amplifiers, generally, which may be used in electrical measuring and testing circuits, particularly subclass 2 for amplifier condition testing or measuring. Where the amplifier is used merely as a part of an arrangement to measure or test a condition other than that of the amplifier, itself, classification is not in Class 330 but in the appropriate subclass of Class 324.
331Oscillators,   subclass 44 for oscillator systems provided with frequency calibrating or testing means, and subclass 64 for oscillator systems provided with indicator, signal or alarm.
332Modulators,   appropriate subclasses particularly subclasses 118 and 150 for the modulators having indicating, observing and/or signaling means.
333Wave Transmission Lines and Networks,   appropriate subclasses, particularly subclasses 2+ , 14 and 17.1+ for the subject matter of that class automatically responsive to a condition.
336Inductor Devices,   subclasses 30+ for the subject matter of that class automatically responsive to a condition.
340Communications: Electrical,   appropriate subclasses, for subject matter sometimes similar to that in Class 324. (See Lines With Other Classes and Within This Class for a further discussion of the line).
343Communications: Radio Wave Antennas,   subclasses 5+ for reflected and/or otherwise returned radio wave energy wave measuring, testing and sensing systems, such as RADAR and ponder systems, and subclasses 350+ for direction finding radio systems.
346Recorders,   for recorders which record the operation of machines or workmen. Many of these recorders, especially in subclasses 33+ record the result of a measurement, test or sensing operation. Generally, but not invariably, a Class 324 disclosure, when combined with a recorder, is classified in Class 324.
348Television,   subclasses 180+ for monitoring, testing, or measuring television signals or apparatus.
356Optics: Measuring and Testing,   for measuring and testing light, materials and articles by means of visible light particularly subclasses 23+ for optical stroboscopes, subclasses 27+ for velocity or velocity and height measurements, subclasses 213+ for photometers, subclasses 237.1+ for apparatus for flaw detection subclasses 300+ for spectroscopic examination, subclasses 432+ for light transmission tests and subclasses 445+ for light reflection tests.
361Electricity: Electrical Systems and Devices,   subclasses 1+ for safety systems responsive to an unsafe condition, such as circuit breaker systems, and subclasses 236+ for speed responsive electrical systems.
363Electric Power Conversion Systems,   subclasses 74 , 164 and 165 for the subject matter of that class automatically responsive to a condition.
365Static Information Storage and Retrieval,   subclass 200 wherein a defective memory device is used to store information, subclass 201 for specifics of a memory device which is tested for defects or erroneous information.
368Horology: Time Measuring Systems or Devices,   subclasses 155+ for time measuring by clocks having electrical features.
374Thermal Measuring and Testing,   appropriate subclasses for a measurement or test of a thermal quantity, whether performed electrically or nonelectrically, except for a measurement or test involving a particle spin determination.
376Induced Nuclear Reactions: Processes, Systems, and Elements,   subclasses 245+ for processes or device for testing, measuring, etc., of a condition of a nuclear reactor during its operation.
378X-Ray or Gamma Ray Systems or Devices,   appropriate subclasses, particularly subclasses 44+ , 51+ and 70+ for X-ray systems used in testing.
379Telephonic Communications,   appropriate subclasses, particularly subclasses 1.01 through 35,for telephony combined with electrical measuring, testing or sensing.
422Chemical Apparatus and Process Disinfecting, Deodorizing, Preserving, or Sterilizing,   subclasses 50+ and 105+ for apparatus for electrical measuring, testing, or sensing combined with significant chemical reaction or control.
429Chemistry: Electrical Current Producing Apparatus, Product and Process,   subclasses 61+ for automatic battery control means combined with the battery, and subclasses 90+ for battery having measuring, testing, and indicating means. (See Lines With Other Classes and Within This Class for further discussion of the line between Class 429 and Class 324.)
434Education,   and Demonstration appropriate subclasses, for electrical measuring, testing or sensing in combination with education.
436Chemistry: Analytical and Immunological Testing,   subclasses 1+ for processes of electrical measuring, testing, or sensing combined with significant chemical reaction or control.
439Electrical Connectors,   subclasses 488+ for a connector having indicating means or identifying means.
455Telecommunications,   appropriate subclasses for radio systems having electrical measuring testing or sensing means for indicating the operative condition of the radio system.
473Games Using Tangible Projectile,   and its incorporated class (273, Amusement Devices: Games), for a game device or apparatus (e.g., a pin-ball machine, target range, aerial projectile target device, bowling alley apparatus, golfing apparatus, simulated game apparatus, chance device, etc.) which may have an electrical indicator.
505Superconductor Technology: Apparatus, Material, Process,   subclasses 150+ for high temperature (Tc greater than 30 K) superconducting device, and particularly subclasses 160+ for measuring or testing system or device; and subclass 310 for a process of measuring or testing a superconductive property.
702Data Processing: Measuring, Calibrating, or Testing,   appropriate subclasses for data processing systems or calculating computers which are utilized for testing, measuring, or monitoring the operation of an external device or quantity where the external device or quantity must be only nominally claimed, particularly subclasses 6 through 13for well-logging, subclasses 14-18 for seismology, subclasses 57-80 for electrical signal parameter measurement, subclasses 85-107 for calibration, subclasses 108-126 for a testing system, subclass 141 for acceleration, subclasses 142-149 for speed or velocity, subclasses 176-178 for time duration or rate, and subclasses 191-195 for noise reduction in measured signal processing.
703Data Processing: Structural Design, Modeling, Simulation, and Emulation,   subclass 4 for analog simulation of electrical device or system.
714Error Detection/Correction and Fault Detection/Recovery,   appropriate subclasses for error detection, correction, recovery or prevention in pulse code data or computers.

SUBCLASSES

[List of Patents for class 324 subclass 66]    66
 This subclass is indented under the class definition.  Subject matter for determining the location of a particular conductor or for identifying a particular conductor out of many.
(1) Note. This subclass includes, for example, the determination of a particular phase of polyphase conductors.

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379Telephonic Communications,   subclasses 1.01 through 35,for testing devices used in telephony to identify or locate a particular line.
  
[List of Patents for class 324 subclass 67]    67
 This subclass is indented under subclass 66.  Subject matter for determining the location of a conductor at a point which is inaccessible.
(1) Note. The conductor, for example, may be located in a conduit inside a wall.

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326+,for similar subject matter utilized to determine the location of conductors which are buried in the earth.
  
[List of Patents for class 324 subclass 71.1]    71.1DETERMINING NONELECTRIC PROPERTIES BY MEASURING ELECTRIC PROPERTIES:
 This subclass is indented under the class definition.  Subject matter for determining a nonelectric property by measuring an electric property.

SEE OR SEARCH THIS CLASS, SUBCLASS:

61,for the determination of a nonelectric property by measuring capacity.
65,for the determination of a nonelectric property by measuring resistance.
  
[List of Patents for class 324 subclass 71.2]    71.2Erosion:
 This subclass is indented under subclass 71.1.  Subject matter where the nonelectric property measured relates to the amount of material removed from an object.
  
[List of Patents for class 324 subclass 71.3]    71.3Beam of atomic particles:
 This subclass is indented under subclass 71.1.  Subject matter where the property being measured is some characteristic of a beam of atomic particles.
  
[List of Patents for class 324 subclass 71.4]    71.4Particle counting:
 This subclass is indented under subclass 71.1.  Subject matter where the measurement means includes means for counting particles.
(1) Note. For classification in this subclass there should be recited significant details in regard to handling or preparing the particles to be counted.

SEE OR SEARCH CLASS:

377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   subclasses 10+ for particle counting, per se, and see also the search notes thereunder.
  
[List of Patents for class 324 subclass 71.5]    71.5Semiconductors for nonelectrical property:
 This subclass is indented under subclass 71.1.  Subject matter including semiconductive means for sensing variations in the nonelectrical property being measured.

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438Semiconductor Device Manufacturing: Process,   subclasses 17+ for methods of making semiconductor electrical devices combined with measurement of an electrical condition.
  
[List of Patents for class 324 subclass 71.6]    71.6Superconductors:
 This subclass is indented under subclass 71.1.  Subject matter where the nonelectric properties being determined are those of superconductors.
  
[List of Patents for class 324 subclass 72]    72
 This subclass is indented under the class definition.  Subject matter for determining voltage, phase, current, power, frequency or a related quantity in a specific environment.
(1) Note. This subclass includes, for example, voltmeters, per se, in combination with a specific lightning rod.

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76+,for a measurement of electricity, per se, when not related to a specific environment. Note particularly subclass 157 for the measurement of electricity combined with some other feature. See (3) Note to the definition of subclass 76 for a statement of the line between subclasses 72 and 76.
  
[List of Patents for class 324 subclass 72.5]    72.5
 This subclass is indented under subclass 72.  Subject matter having a voltage probe.

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119,for volt meters and ammeters having rectifiers in a probe.
149,for voltmeters and ammeters having a probe.

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439Electrical Connectors,   appropriate subclasses for probe conductor structure, per se.
  
[List of Patents for class 324 subclass 73.1]    73.1PLURAL, AUTOMATICALLY SEQUENTIAL TESTS:
 This subclass is indented under the class definition.  Subject matter for measuring or determining two or more electrical characteristics of an electrical circuit or circuit element, or for measuring or determining a single electrical characteristic of two or more electrical circuits or circuit elements, wherein the measurements or determinations are made one after another without human intervention.
(1) Note. This subclass is the residual locus of processes and apparatus which automatically perform sequential tests of the Class 324 type, none of which tests are provided for by subclasses preceding this one in the Class 324 schedule. Similar processes and apparatus in which one of the plural tests is provided for in a preceding subclass will be found in that subclass. For example, a patent claiming means for automatically testing a circuit for an "open circuit" caused by the failure of a circuit element, followed automatically by a test to determine the input/output characteristics of the circuit is classifiable as an "original" in subclasses 500+.
(2) Note. This subclass is the locus of processes and apparatus for performing, in automatic sequence, two or more Class 324 type tests which otherwise may be provided for in subclasses following this one in the Class 324 schedule. For example, a patent claiming a testing apparatus consisting of a combination of means to determine frequency, means to compare phase, and means to permit a human operator to switch from one means to another is classifiable as an "original" in subclasses 78+.
(3) Note. Subject matter for performing plural, Class 324 type tests simultaneously but not sequentially will be found in subclasses determined by the tests, per se.
(4) Note. Electrical characteristics measured by the subject matter of this subclass type include the response of a circuit or circuit element to a particular electrical input and includes such tests to determine the existence of miswired circuits. For similar subject matter used to detect the presence of short or open circuits caused by failures in circuit elements or their interconnections, see the reference below to subclasses 500+ in the search notes to other subclasses in this class.
(5) Note. The measurements of this subclass type may result in either quantitative or qualitative ("go-no-go") indications.
(6) Note. The automatic, sequential measurement of the analog responses of a circuit or circuit element to two different input levels is classifiable in this subclass. The response of a circuit or circuit element to a pattern of high and low digital input signals is classifiable in Class 371.
(7) Note. Testing means of this subclass type produce a distinct indication for each of the plural tests, Hence, testing means comprising plural transducers or detectors, each of outputs are combined to produce only on indication is not classifiable in this subclass unless the whole test is automatically repeated.

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114,for plural tests employing plural meters, which tests are not automatically sequenced.
115+,for plural tests employing plural meter ranges, which tests are not automatically sequenced.
133,for plural go-no-go tests which are not automatically sequenced.
140,for testing means having plural inputs, which means does not include automatic sequencing.
459+,for measuring or testing electrical parameters of printed circuits with an ionizable gas.
500+,for plural tests explicitly for the purpose of detecting failures in circuits or circuit elements consisting of open or short circuits.
754.01through 755.11 for test probe techniques.

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209Classifying, Separating, and Assorting Solids,   especially subclass 556 , for diverse electrical test used to classify, separate or sort articles, and subclasses 571+ for sorting by sensing properties of articles by electrical testing means.
250Radiant Energy,   subclasses 306+ for plural sequential tests involving testing by charged particles, especially subclass 310 for automatic sequential tests of printed circuits using an electron probe, and subclasses 363+ for automatic sequential tests of electrical circuits and devices using radiant energy and invisible-to-visible light converters.
340Communications: Electrical,   subclass 653 for electrical alarms responsive to circuits for testing electrical circuits or components.
382Image Analysis,   appropriate subclasses for automatic, sequential tests of printed circuits using image comparison.
455Telecommunications,   subclasses 115.1 through 115.4and subclasses 226.1-226.4 for the testing of radio transmitters and receivers, respectively, which may include automatic sequential tests.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 108+ for testing systems, particularly subclasses 117+ for testing of circuits, subclass 118 for testing multiple circuits, and subclass 121 for multiple test instruments.
714Error Detection/Correction and Fault Detection/Recovery,   appropriate subclasses for error detection, correction, recovery or prevention in pulse code data or computers.
  
[List of Patents for class 324 subclass 74]    74
 This subclass is indented under the class definition.  Subject matter for testing and calibrating electric meters.

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130,for electric meters, per se, having self-calibrating features.

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73Measuring and Testing,   subclasses 1.01+ , for the proving or calibrating of mechanical instruments.
374Thermal Measuring and Testing,   subclasses 1+ for calibration or testing of a thermally responsive instrument.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 85+ for calibration or correction system, subclasses 108+ for testing systems.
  
[List of Patents for class 324 subclass 75]    75
 This subclass is indented under subclass 74.  Subject matter in which the testing or calibrating is done by stroboscopic means.

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315Electric Lamp and Discharge Devices: Systems,   appropriate subclasses, for flashing lamp systems.
356Optics: Measuring and Testing,   subclasses 23+ for optical stroboscopes.
  
[List of Patents for class 324 subclass 76.11]    76.11MEASURING, TESTING, OR SENSING ELECTRICITY, PER SE:
 This subclass is indented under the class definition.  Subject matter relating to the measurement of electric voltages or currents, or combinations thereof, when said electric voltages and currents do not occur in a significantly recited external environment.
(1) Note. Measurement requires sensing and some indication of the result of the sensing. The indication can be quantitative, as in a calibrated voltmeter, or qualitative, as in an uncalibrated cathode-ray oscilloscope or a "hot line" indicator. No distinction is made in these subclasses between testing and measuring.
(2) Note. The definition is not limited to subject matter which indicates the result of the measurement, but covers the sensing subcombination as well. Such subcombinations, when disclosed as having utility only in the measurement of this subclass, are generally classified here, but when disclosed to a specific art device, are classified in one of the classes referred to under the search notes.
(3) Note. The recited external environment is significant to the measurement when there is a disclosed significant relation or when the claims recite, by more than name only, more of the environment than is necessary for the performance of the measurement. When the external environment is not significant, for example, a meter which indicates the phase difference between A-C voltages in different circuits, will be classified in this class even though one of the inputs is recited as being from a generator and the other as being from a power system.

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72,for this subject matter in combination with a specific environment. See (3) Note above.

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73Measuring and Testing,   appropriate subclasses for nonelectrical measuring and testing and for electrical measuring and testing in combination with non-electrical measuring and testing. See the proceeding Class 324 definition notes for specific subclasses.
315Electric Lamp and Discharge Devices: Systems,   subclasses 1+ for cathode-ray tube circuits of general application, including those for producing a visual grid on the face of the tube for calibration purposes.
340Communications: Electrical,   subclasses 870.01+ for telemetering systems for indicating at a remote point the value of a local condition. Class 324 provides for significant measuring, testing, or sensing of electricity, per se, and the indication of the result, whether by a telemetering system or otherwise.
356Optics: Measuring and Testing,   appropriate subclasses for measuring and testing light.
362Illumination,   subclasses 23.01 through 23.22for illuminated dial or scale, some of which can be used as voltage or current indicators.
370Multiplex Communications,   subclasses 241+ for testing (other than synchronization) of a multiplex communication element.
374Thermal Measuring and Testing,   appropriate subclasses for thermal measuring and testing.
375Pulse or Digital Communications,   subclasses 224+ for measuring and testing of pulse or digital communications device.
379Telephonic Communications,   subclasses 1.01 through 35for diagnostic testing, malfunction indication, or electrical condition measurement of a telephonic communication device.
455Telecommunications,   subclasses 115.1 through 115.4for measuring and testing of a transmitter and subclasses 226.1-226.4 for measuring and testing of a receiver in telecommunications.
714Error Detection/Correction and Fault Detection/Recovery,   appropriate subclasses for error detection, correction, recovery or prevention in pulse code data or computers.
  
[List of Patents for class 324 subclass 76.12]    76.12Analysis of complex waves:
 This subclass is indented under subclass 76.11.  Subject matter whereby one or more components of a periodic wave made up of a combination of several frequencies or several sine waves superimposed on one another has components which are examined.
(1) Note. Such analysis as is found in this subclass is usually referred to as Fourier analysis.

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76.39+,for the measurement of frequency of a cyclic current or voltage, per se.
76.77+,for the measurement of phase of cyclic voltage or current.

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73Measuring and Testing,   subclass 861.06 for volume or rate of flow meters measuring transit time of a tracer or tag by correlator means.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 66+ for wave form analysis, particularly subclass 77 for Fourier analysis, subclass 112 for a testing system having sinusoidal signal stimulus, and subclasses 124+ for signal generation or waveform shaping.
704Data Processing: Speech Signal Processing, Linguistics, Language Translation, and Audio Compression/Decompression,   subclasses 205+ for determination of the component frequencies in a speech signal.
  
[List of Patents for class 324 subclass 76.13]    76.13Amplitude distribution:
 This subclass is indented under subclass 76.12.  Subject matter comprising means to measure an extent of dispersion of magnitude variation in the component of the complex wave.
(1) Note. The amplitudes may be statistically analyzed.
  
[List of Patents for class 324 subclass 76.14]    76.14Radiometer (e.g., microwave, etc.):
 This subclass is indented under subclass 76.13.  Subject matter having means that detect and measure radiant energy either at separate wave lengths or integrated over a broad wavelength band in the complex wave.

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76.56,for microwave frequency detection in digital output used in determining the frequency of cyclic current or voltage.

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250Radiant Energy,   subclass 250 for the measurement of radio or microwaves by an absorption wavemeter
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   appropriate subclasses for directive radio wave systems and devices used in communication.
  
[List of Patents for class 324 subclass 76.15]    76.15With sampler:
 This subclass is indented under subclass 76.13.  Subject matter including a device whose output is a series of discrete values representative of the values of an input at a series of points in time.

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76.24,for sampling in a frequency spectrum analyzer.
76.38,for sampling, per se, in analysis of complex waves.
76.42,for sampling by frequency comparison in frequency of cyclic current or voltage.
76.58,for sampling in digital output by phase comparison.
  
[List of Patents for class 324 subclass 76.16]    76.16With counter:
 This subclass is indented under subclass 76.13.  Subject matter including a device capable of changing stages in a specified sequence upon receiving appropriate signals.

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76.48,for counters in digital output by frequency comparison used to determine the frequency of cyclic current or voltage.
76.62,for counters in digital output by phase comparison used to determine the frequency of cyclic current or voltage.

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377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   subclass 19 where pulses are counted in systems for determining the value of some parameters.
  
[List of Patents for class 324 subclass 76.17]    76.17With integrator:
 This subclass is indented under subclass 76.13.  Subject matter whereby summing of a signal is derived.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 336+ for miscellaneous integrating circuits.
708Electrical Computers: Arithmetic Processing and Calculating,   subclasses 823+ for analog integrators, per se.
  
[List of Patents for class 324 subclass 76.18]    76.18With slope detector:
 This subclass is indented under subclass 76.13.  Subject matter comprising means to monitor the rise over the run in a wave.

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76.25,for slope detection in frequency spectrum analyzers.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 14+ for miscellaneous slope detecting circuits and subclass 170 for slope control of a pulse waveform.
  
[List of Patents for class 324 subclass 76.19]    76.19Frequency spectrum analyzer:
 This subclass is indented under subclass 76.12.  Subject matter including means that show an energy distribution as a function of frequency for a given signal.

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702Data Processing: Measuring, Calibrating, or Testing,   subclasses 76+ for frequency spectrum analysis.
  
[List of Patents for class 324 subclass 76.21]    76.21By Fourier analysis:
 This subclass is indented under subclass 76.19.  Subject matter wherein the energy distribution is taken at discrete harmonic components, i.e., harmonics, of the given signal.

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702Data Processing: Measuring, Calibrating, or Testing,   subclass 77 for Fourier analysis in a waveform measuring system.
708Electrical Computers: Arithmetic Processing and Calculating,   subclasses 823+ for analog integrators, per se.
  
[List of Patents for class 324 subclass 76.22]    76.22Real-time spectrum analyzer:
 This subclass is indented under subclass 76.19.  Subject matter including a device which operates with sufficient speed that the energy distribution is determined within set timing limits.
  
[List of Patents for class 324 subclass 76.23]    76.23With mixer:
 This subclass is indented under subclass 76.19.  Subject matter including a circuit that generates output frequencies equal to the sum or difference of two input frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.43,for plural mixers used in frequency comparison for the determination of cyclic current or voltage.

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455Telecommunications,   subclasses 313+ for mixers, per se.
  
[List of Patents for class 324 subclass 76.24]    76.24With sampler:
 This subclass is indented under subclass 76.19.  Subject matter including a device whose output is a series of discrete values representative of the values of an input at a series of points in time.

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76.15,for sampling used in Amplitude distribution devices.
76.38,for sampling, per se, in analysis of complex waves.
76.42,for sampling by frequency comparison in determination of frequency of cyclic current or voltage.
76.58,for sampling in digital output by phase comparison in determination of frequency of cyclic current or voltage.
  
[List of Patents for class 324 subclass 76.25]    76.25With slope detector:
 This subclass is indented under subclass 76.19.  Subject matter comprising means to monitor the rise over the run in a wave.

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76.18,for slope detection in amplitude distribution.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 14+ for miscellaneous slope detecting circuits and subclass 170 for slope control of a pulse waveform.
  
[List of Patents for class 324 subclass 76.26]    76.26Scanning-panoramic receiver:
 This subclass is indented under subclass 76.19.  Subject matter including a radio receiver that displays, on the screen of a cathode-ray tube, the presence and relative strength of all signals within a wide frequency range.

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315Electric Lamp and Discharge Devices: Systems,   subclasses 364+ for cathode-ray tube deflections circuits.
455Telecommunications,   subclasses 145+ for panoramic display, per se.
  
[List of Patents for class 324 subclass 76.27]    76.27With particular sweep circuit:
 This subclass is indented under subclass 76.26.  Subject matter including a specific circuit which produces at regular intervals, an approximately linear, circular, or other movement of a beam in a cathode-ray tube.
  
[List of Patents for class 324 subclass 76.28]    76.28Digital filter:
 This subclass is indented under subclass 77.11.  Subject matter wherein an input signal is operated on by means of digital circuitry to alter the frequency spectrum of the input signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.29,for filtering in frequency spectrum analyzers.
76.31,for parallel filters in frequency spectrum analysis.
76.44,for filtering in frequency comparison used to determine the frequency of cyclic current or voltage.
76.68,for filtering in phase comparison used to determine the frequency of cyclic current or voltage.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   appropriate subclasses for filters and filtering in wave transmission lines and networks.
702Data Processing: Measuring, Calibrating, or Testing,   subclass 17 for filtering or noise removal in a seismic prospecting system, subclasses 190+ for measured signal extraction or separation (e.g., filtering).
  
[List of Patents for class 324 subclass 76.29]    76.29With filtering:
 This subclass is indented under subclass 77.11.  Subject matter including a network of resistors, inductors, or capacitors which offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.44+,for filtering in frequency comparison for determination of the frequency of cyclic current or voltage.
76.68,for filtering in phase comparison for the determination of the frequency of cyclic current or voltage.

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333Wave Transmission Lines and Networks,   appropriate subclasses for filters and filtering in wave transmission lines and networks.
702Data Processing: Measuring, Calibrating, or Testing,   subclass 17 for filtering or noise removal in a seismic prospecting system, subclasses 190+ for measured signal extraction or separation (e.g., filtering).
  
[List of Patents for class 324 subclass 76.31]    76.31Parallel filters:
 This subclass is indented under subclass 76.29.  Subject matter including parallel connected network of resistors, inductors, or capacitors which offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.28,for digital filters in frequency spectrum analysis.
76.44,for filtering in frequency comparison used to determine the frequency of cyclic current or voltage.
76.68,for filtering in phase comparison used to determine the frequency of cyclic current or voltage.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   appropriate subclasses for filters and filtering in wave transmission lines and networks.
702Data Processing: Measuring, Calibrating, or Testing,   subclass 17 for filtering or noise removal in a seismic prospecting system, subclasses 190+ for measured signal extraction or separation (e.g., filtering).
  
[List of Patents for class 324 subclass 76.32]    76.32With space discharge device:
 This subclass is indented under subclass 76.31.  Subject matter comprising any device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.76,for space discharge device in frequency of cyclic current or voltage devices.

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313Electric Lamp and Discharge Devices,   for space discharge devices, per se.
  
[List of Patents for class 324 subclass 76.33]    76.33Correlation:
 This subclass is indented under subclass 77.11.  Subject matter including means to measure the similarity of two or more signals.

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708Electrical Computers: Arithmetic Processing and Calculating,   subclasses 422+ for correlation in electric digital calculating computers.
  
[List of Patents for class 324 subclass 76.34]    76.34With space discharge device:
 This subclass is indented under subclass 76.33.  Subject matter comprising any device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.

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76.76,for space discharge device in frequency of cyclic current or voltage devices.

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313Electric Lamp and Discharge Devices,   for space.
  
[List of Patents for class 324 subclass 76.35]    76.35With delay line:
 This subclass is indented under subclass 77.11.  Subject matter comprising a real or artificial transmission line or equivalent component that slows a signal for a predetermined length of time.

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76.54,for delay line in phase comparison in frequency of cyclic current or voltage.

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333Wave Transmission Lines and Networks,   appropriate subclasses for delay lines in wave transmission lines and networks.
  
[List of Patents for class 324 subclass 76.36]    76.36With optics:
 This subclass is indented under subclass 77.11.  Subject matter comprising lenses, prisms, or mirrors to be used in the frequency spectrum analyzer.

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356Optics: Measuring and Testing,   for optics measuring and testing, per se.
359Optics: Systems (Including Communication) and Elements,   appropriate subclasses for optical systems and devices that may be used in measuring and testing.
  
[List of Patents for class 324 subclass 76.37]    76.37Bragg cell:
 This subclass is indented under subclass 76.36.  Subject matter comprising acousto-optic means to redirect light by the method of Bragg diffraction.
  
[List of Patents for class 324 subclass 76.38]    76.38With sampler:
 This subclass is indented under subclass 76.12.  Subject matter including a device whose output is a series of discrete values representative of the values of an input at a series of points in time.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.15,for sampling in amplitude distribution devices.
76.24,for sampling in a frequency spectrum analyzer.
76.42,for sampling by frequency comparison in frequency of cyclic current or voltage.
76.58,for sampling in digital output by phase comparison.
  
[List of Patents for class 324 subclass 76.39]    76.39Frequency of cyclic current or voltage (e.g., cyclic counting etc.):
 This subclass is indented under subclass 76.11.  Subject matter relating to the measuring of the frequency of an electric voltage or current which fluctuates in a periodic manner.
(1) Note. Generally, when an intangible electric voltage measurement occurs in a significant environment (for example, when the measurement is of the synchronizing frequency in a communication system) the class which provides for the environment also provides for the frequency measurement in that environment. The search should therefore, in appropriate instances, extend to other classes. An environment recited by name only is not considered to be significant.
(2) Note. The frequency measurement may be indicated in various manners, as in terms of frequency error, deviation, or average frequency over a period of time. The measurement and indication may be either qualitative or quantitative.
(3) Note. It is impossible to vary the frequency of a periodically varying voltage without concomitantantly varying its phase. Consequently, when the frequency changes slowly, it may be possible to indicate frequency by measuring phase angle. In those instances the search should extend to subclasses 76.77+, especially subclass 91, since synchronization is usually concerned with obtaining a zero phase angle rather than with obtaining a mere equality of frequency.

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160+,for electrical measuring of speed, for example, the speed of rotating shafts or bullets, and for measuring the average frequency of random events, such as the occurrence of random electrical impulses and for timing means utilized to electrically determine the time interval between points spaced in time, when said points are not determined by the fluctuations of a periodically varying voltage, as when the points are determined, for example, by a randomly varying voltage or by the events at a race track.
76.12+,for complex wave analysis, per se.

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84Music,   subclasses 454+ for tuning devices utilized in the tuning of musical instruments, some of which will measure the frequency of an unknown sound.
250Radiant Energy,   subclass 250 for the measurement of radio or microwaves by an absorption wavemeter.
329Demodulators,   subclasses 311+ for pulse demodulators or detectors; subclasses 315+ for frequency demodulators; and subclasses 345+ for phase demodulators.
331Oscillators,   subclass 44 for oscillators provided with means or the method for calibrating the oscillator with respect to its generated frequency and subclass 64 for oscillators.
332Modulators,   subclass 118 for frequency modulators having frequency measuring means and for the frequency meters, per se, when limited to use with modulation.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   appropriate subclasses for radar systems. Note particularly subclasses 104+ for such systems (for example, by measuring the frequency shift due to the doppler effect) and subclasses 128+ for such systems which utilize frequency modulated waves.
361Electricity: Electrical Systems and Devices,   subclasses 236+ for speed sensing and speed controlled systems, such as synchronizing systems.
368Horology: Time Measuring Systems or Devices,   subclasses 15+ and 155+ for clocks which serve as standards in frequency measurements.
377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   appropriate subclasses for frequency of cyclic current or voltage in cycle counters or cycle counting.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 75+ for frequency analysis, subclass 106 for signal frequency or phase correction.
  
[List of Patents for class 324 subclass 76.41]    76.41Frequency comparison (e. g., heterodyne, etc.):
 This subclass is indented under subclass 76.39.  Subject matter having means to compare two frequencies with each other.
(1) Note. The two frequencies are usually, but not necessarily, sinusoidal.
(2) Note. One frequency, for example, may serve as a time base for an oscilloscope upon which the other frequency is displayed, or the two frequencies may be heterodyned to make a beat which has a mathematically determinable frequency with respect to the two frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.77+,especially subclass 91, for this subject matter when the frequency comparison is for synchronizing purposes. See also (3) Note to subclass 76.39.

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315Electric Lamp and Discharge Devices: Systems,   subclasses 1+ for cathode-ray tube circuits that can be used in frequency comparison (e.g., oscilloscopes, etc.).
331Oscillators,   for oscillators whose generated frequency can be varied or which can serve as frequency standards. By way of example, subclasses 37+ of Class 331 provides for beat frequency oscillator systems, and subclass 44 provides for oscillators with frequency calibration of oscillator.
334Tuners,   appropriate subclasses for tuned networks for use in wave energy apparatus and comprising inductance and capacitance elements in circuit arrangement to form a resonant circuit and in which structure is provided for adjusting one or both of these elements for changing the mean resonant frequency of the circuit. Note especially subclasses 30+ for tuners combined with resonant indicators.
455Telecommunications,   for this subject matter in combination with a radio receiving system, particularly subclasses 145+ for panoramic receivers.
  
[List of Patents for class 324 subclass 76.42]    76.42With sampler:
 This subclass is indented under subclass 76.41.  Subject matter including a device whose output is a series of discrete values representative of the values of an input at a series of points in time.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.15,for sampling in amplitude distribution devices.
76.24,for sampling in a frequency spectrum analyzer.
76.38,for sampling, per se, in analysis of complex waves current, or voltage.
76.58,for sampling in digital output by phase comparison.
  
[List of Patents for class 324 subclass 76.43]    76.43With plural mixers:
 This subclass is indented under subclass 76.41.  Subject matter including more than one circuit that generates output frequencies equal to the sum and the difference of two input frequencies.

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76.23,for mixers in frequency spectrum analyzers

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455Telecommunications,   subclasses 313+ for mixers, per se.
  
[List of Patents for class 324 subclass 76.44]    76.44With filtering:
 This subclass is indented under subclass 76.41.  Subject matter including a selective network of resistors, inductors, or capacitors which offers comparatively little opposition to certain frequencies,while blocking or attenuating other frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.28,for digital filters in frequency spectrum analysis.
76.29+,for filtering in frequency spectrum analyzer.
76.31,for parallel filters in frequency spectrum analysis.
76.68,for filtering in phase comparison used to determine the frequency of cyclic current or voltage.
  
[List of Patents for class 324 subclass 76.45]    76.45Bandpass:
 This subclass is indented under subclass 76.44.  Subject matter that limits the range of frequencies that will be passed through a device.
  
[List of Patents for class 324 subclass 76.46]    76.46Plural:
 This subclass is indented under subclass 76.44.  Subject matter including more than one filter.
  
[List of Patents for class 324 subclass 76.47]    76.47Digital output:
 This subclass is indented under subclass 76.41.  Subject matter comprising an output signal which represents the size of a stimulus or input signal in the form of a series of discrete quantities which are coded to represent digits in a system of numerical notation.

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76.55+,for digital output by phase comparison in frequency of cyclic current or voltage.
76.82+,for digital output in phase comparison, per se.
  
[List of Patents for class 324 subclass 76.48]    76.48With counter:
 This subclass is indented under subclass 76.47.  Subject matter including a device capable of changing stages in a specified sequence upon receiving appropriate signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.16,for counters in amplitude distribution devices.
76.62,for plural counters in digital output by phase comparison.

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377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   subclass 19 where pulses are counted in systems for determining the value of some parameters.
  
[List of Patents for class 324 subclass 76.49]    76.49Tuned mechanical resonator (e.g., reed, piezocrystal, etc.):
 This subclass is indented under subclass 76.39.  Subject matter having a mechanical resonating system and an electromechanical transducer to drive the mechanical resonating system in accordance with the electric voltage or current.
(1) Note. The mechanical resonator is usually a reed and its vibration can be visually observed, but it may be a quartz crystal whose motion is not visible or some other resonator.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   subclasses 141+ and 186+ for electromechanical filters utilizing mechanical resonating systems.
  
[List of Patents for class 324 subclass 76.51]    76.51By tuning (e.g., to resonance, etc.):
 This subclass is indented under subclass 76.39.  Subject matter having circuit which may be adjusted for resonance at a particular frequency or other predetermined condition.

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76.41+,for this subject matter in combination with heterodyning means.
76.49+,for this subject matter where the tuned current has a tuned mechanically resonant element.

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250Radiant Energy,   subclass 250 for this subject matter in combination with a radio or carrier wave communication frequency
334Tuners,   appropriate subclasses for tuned networks for use in wave energy apparatus and comprising inductance and capacitance elements in circuit arrangement to form a resonant circuit and in which structure is provided for adjusting one or both of these elements for changing the mean resonant frequency of the circuit.
455Telecommunications,   subclasses 154.1+ for indicator means combined with frequency selection means in a radio receiver.
  
[List of Patents for class 324 subclass 76.52]    76.52By phase comparison:
 This subclass is indented under subclass 76.39.  Subject matter having angle relationship means as a part thereof, in order to perform the frequency measurement.

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76.77+,for the phase comparison means, per se.
  
[List of Patents for class 324 subclass 76.53]    76.53With phase lock:
 This subclass is indented under subclass 76.52.  Subject matter comprising means of making the phase of an oscillator signal follow exactly the phase of a reference signal.
  
[List of Patents for class 324 subclass 76.54]    76.54With delay line:
 This subclass is indented under subclass 76.52.  Subject matter comprising a real or artificial transmission line or equivalent component that slows a signal for a predetermined length of time.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.35,for delay line in frequency spectrum analyzer.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   appropriate subclasses for delay lines in wave transmission lines and networks.
  
[List of Patents for class 324 subclass 76.55]    76.55Digital output:
 This subclass is indented under subclass 76.52.  Subject matter comprising an output signal which represents the size of a stimulus or input signal in the form of a series of discrete quantities which are coded to represent digits in a system of numerical notation.

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76.47+,for digital output in frequency comparison.
76.82,for digital output in phase comparison, per se.
  
[List of Patents for class 324 subclass 76.56]    76.56With microwave frequency detection:
 This subclass is indented under subclass 76.55.  Subject matter comprising means to detect frequencies of 1000mhz plus.

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76.14,for radiometers in amplitude distribution used in analysis of complex waves.

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250Radiant Energy,   subclass 250 for the measurement of radio or microwaves by an absorption wavemeter.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   appropriate subclasses for directive radio wave systems and devices used in communication.
  
[List of Patents for class 324 subclass 76.57]    76.57With tone detection:
 This subclass is indented under subclass 76.55.  Subject matter comprising means to detect a sound sensation having pitch.
  
[List of Patents for class 324 subclass 76.58]    76.58With sampler:
 This subclass is indented under subclass 76.55.  Subject matter including a device whose output is a series of discrete values representative of the values of an input at a series of points in time.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.15,for sampling in amplitude distribution devices.
76.24,for sampling in a frequency spectrum analyzer.
76.38,for sampling used in analysis of complex waves.
76.42,for sampling in frequency comparison used in determination of frequency of cyclic current or voltage.
  
[List of Patents for class 324 subclass 76.59]    76.59With multiplexing:
 This subclass is indented under subclass 76.55.  Subject matter including a device for simultaneous transmission of two or more signals in either or both directions over the same transmission path.

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370Multiplex Communications,   for multiplex communications, per se.
  
[List of Patents for class 324 subclass 76.61]    76.61With memory:
 This subclass is indented under subclass 76.55.  Subject matter comprising means to collect and hold information until it is needed.

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365Static Information Storage and Retrieval,   for memories, per se.
  
[List of Patents for class 324 subclass 76.62]    76.62With counter:
 This subclass is indented under subclass 76.55.  Subject matter including devices capable of changing stages in a specified sequence upon receiving appropriate signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.16,for counters in amplitude distribution devices.
76.48,for counters in digital output by frequency comparison used in determining the frequency of cyclic current or voltage.

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377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   subclass 19 where pulses are counted in systems for determining the value of some parameters.
  
[List of Patents for class 324 subclass 76.63]    76.63Using register:
 This subclass is indented under subclass 76.62.  Subject matter including a device in which information is stored in and serially transferred through a storage medium.

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235Registers,   for mechanical registers, per se.
377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   for electrical registers, per se.
  
[List of Patents for class 324 subclass 76.64]    76.64Plural:
 This subclass is indented under subclass 76.62.  Subject matter comprising more than one counter.
  
[List of Patents for class 324 subclass 76.65]    76.65With space discharge device:
 This subclass is indented under subclass 76.55.  Subject matter comprising any device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.76,for space discharge device in frequency of cyclic current or voltage devices.

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313Electric Lamp and Discharge Devices,   for space discharge devices, per se.
  
[List of Patents for class 324 subclass 76.66]    76.66With capacitive energy storage:
 This subclass is indented under subclass 76.52.  Subject matter comprising conductors and dielectrics that store electrical energy.
  
[List of Patents for class 324 subclass 76.67]    76.67With space discharge device:
 This subclass is indented under subclass 76.66.  Subject matter comprising any device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.76,for space discharge device in frequency of cyclic current or voltage devices.

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313Electric Lamp and Discharge Devices,   for space discharge devices, per se.
  
[List of Patents for class 324 subclass 76.68]    76.68With filtering:
 This subclass is indented under subclass 76.52.  Subject matter including a network of resistors, inductors, or capacitors which offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.28,for digital filters in frequency spectrum analysis.
76.29+,for filtering in frequency spectrum analyzer.
76.31,for parallel filters in frequency spectrum analysis.
76.44,for filtering in frequency comparison used to determine the frequency of cyclic current or voltage.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   appropriate subclasses for filters and filtering in wave transmission lines and networks.
702Data Processing: Measuring, Calibrating, or Testing,   subclass 17 for filtering or noise removal in a seismic prospecting system, subclasses 190+ for measured signal extraction or separation (e.g., filtering).
  
[List of Patents for class 324 subclass 76.69]    76.69Current output proportional to frequency:
 This subclass is indented under subclass 76.52.  Subject matter whereby the current is related to the frequency by a constant.
  
[List of Patents for class 324 subclass 76.71]    76.71Nulling circuit:
 This subclass is indented under subclass 76.52.  Subject matter comprising a circuit that indicates when current, voltage, or power is zero.
  
[List of Patents for class 324 subclass 76.72]    76.72Qualitative output:
 This subclass is indented under subclass 76.52.  Subject matter whereby an output indicates conformance to specifications of a device.
(1) Note. This is usually a go or no situation.
  
[List of Patents for class 324 subclass 76.73]    76.73With saturable device:
 This subclass is indented under subclass 76.52.  Subject matter comprising a magnetic-core reactor, the reactance of which is controlled by changing the saturation of the core by varying a superimposed unidirectional flux.

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76.75,for inductive sensing used in determining the frequency of cyclic current or voltage.

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307Electrical Transmission or Interconnection Systems,   subclasses 401+ for Nonlinear Reactors Systems (e.g., Saturable), per se.
  
[List of Patents for class 324 subclass 76.74]    76.74Deviation measurement:
 This subclass is indented under subclass 76.52.  Subject matter comprising a device that measures the difference between the actual and specified values of a quantity.
  
[List of Patents for class 324 subclass 76.75]    76.75Having inductive sensing:
 This subclass is indented under subclass 76.39.  Subject matter comprising detecting means which senses an inductance or detects the inducing of a voltage through mutual or electrostatic induction.

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76.73,for a saturable device in by phase comparison used in determining the frequency of cyclic current or voltage.
200+,for devices and methods to sense and indicate the sensing of a magnetic field, per se.
  
[List of Patents for class 324 subclass 76.76]    76.76With space discharge device:
 This subclass is indented under subclass 76.39.  Subject matter comprising any device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.65,for space discharge device in digital output by phase comparison.

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313Electric Lamp and Discharge Devices,   for space discharge devices, per se.
  
[List of Patents for class 324 subclass 76.77]    76.77Phase comparison (e.g., between cyclic pulse voltage and sinusoidal current, etc.):
 This subclass is indented under subclass 76.11.  Subject matter relating to the measuring of a phase relationship between an electric voltage or current which fluctuates in a periodic manner and another electric voltage or current which fluctuates in the same manner.
(1) Note. Generally, when the measurement of an intangible phase relationship occurs in a significant environment (for example, when the measurement is of the phase difference between voltages produced by two generators in an electric generating system) the search is in this class which provides for the phase measurement in that environment. The search should therefore, in appropriate instances, extend to other classes. An environment recited by name only is not considered to be significant.
(2) Note. The voltage or current usually fluctuates in a sinusoidal manner, but may fluctuate in any other periodic manner.
(3) Note. The phase measurement may be indicated in various manners, as in terms of phase angle, power factor, time lag or advance, or otherwise. The measurement and indication may be either quantitative or qualitative (as, for example, "lead" and "lag").
(4) Note. The two periodic voltages or currents need not be supplied to the system as inputs. For example, one of these periodic voltages may be supplied to the system as the unknown input while the other can be derived from the unknown input by an averaging process or can be supplied by a stable oscillator which is part of the system, or it can be supplied by a mechanically moving standard.
(5) Note. It is impossible to vary the phase of a periodically fluctuating voltage or current without concomitantly varying its frequency. Consequently, especially when phase angles vary rapidly, it may be possible to indicate phase angle by measuring frequency. In those instances the search should extend to subclasses 76.39+ of this class.
(6) Note. One of the voltages or currents may be of a different type than the other voltage or current; for example, one may be a sinusoidal voltage while the other may be a pulse current, or one of the voltages may be a harmonic of the other voltage and the measurement may be of the phase relationship between harmonics of the same frequency.

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76.52,for phase comparison in frequency of cyclic current or voltage devices.
141,and 142, for watt meters and voltmeters which do not indicate phase angle but respond to it.
160+,for the measurement of phase angle between an electrical voltage or current and the angular position of a rotating machine which generates or is supplied by said voltage or current.

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329Demodulators,   subclasses 311+ for pulse demodulators using locally generated oscillations, subclasses 336+ for frequency demodulator employing phase shift, and subclass 346 for using locally generated oscillations.
  
[List of Patents for class 324 subclass 76.78]    76.78Quadrature sensing:
 This subclass is indented under subclass 76.77.  Subject matter comprising means to detect the state or condition of two related periodic functions or two related points separated by a quarter of a cycle, or 90 electrical degrees.
  
[List of Patents for class 324 subclass 76.79]    76.79Feedback control, electrical:
 This subclass is indented under subclass 76.77.  Subject matter having electrical means to control a return path from an output terminal to an input terminal of at least one functional circuit device or circuit.

SEE OR SEARCH CLASS:

330Amplifiers,   appropriate subclasses for feedback, per se.
  
[List of Patents for class 324 subclass 76.81]    76.81Feedback control, mechanical:
 This subclass is indented under subclass 76.77.  Subject matter having mechanical means to control a return path from an output terminal to an input terminal of at least one functional circuit device or circuit.

SEE OR SEARCH CLASS:

330Amplifiers,   appropriate subclasses for feedback, per se.
  
[List of Patents for class 324 subclass 76.82]    76.82Digital output:
 This subclass is indented under subclass 76.77.  Subject matter comprising an output signal which represents the size of a stimulus or input signal in the form of a series of discrete quantities which are coded to represent digits in a system of numerical notation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

76.47,for digital output in frequency comparison in frequency of cyclic current or voltage.
76.55,for digital output in by phase comparison in frequency of cyclic current or voltage.
  
[List of Patents for class 324 subclass 76.83]    76.83Analog output:
 This subclass is indented under subclass 76.77.  Subject matter having an output quantity which varies smoothly over a continuous range of values rather than in discrete steps.
  
[List of Patents for class 324 subclass 77.11]    77.11Nonscanning:
 This subclass is indented under subclass 76.19.  Subject matter wherein the frequency components of the spectrum are acquired simultaneously.
  
[List of Patents for class 324 subclass 84]    84
 This subclass is indented under subclass 83.  Subject matter having a wave guide.

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333Wave Transmission Lines and Networks,   subclasses 239+ , for wave guides, per se. Also consult the search notes to that subclass for the other classes which make provision for wave guides.
  
[List of Patents for class 324 subclass 85]    85
 This subclass is indented under subclass 83.  Subject matter having means to change the frequency of a voltage or current into another frequency which varies in correspondence therewith.

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79,for frequency measuring using zero or countable beat heterodyne.
82,for the subject matter of this subclass (85) used to measure frequency.
  
[List of Patents for class 324 subclass 86]    86
 This subclass is indented under subclass 83.  Subject matter in which one of the electric voltages or currents is obtained from a polyphase source.
(1) Note. In order that a disclosure be classified in this subclass, the polyphase source must be significantly related to the phase measurement. For example, the average phase angle of three phases of a three phase circuit may be compared with the phase of a single phase circuit. A polyphase source which supplies only a single phase voltage or current to the measuring equipment, without more, is not significantly related to the phase measurement.

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108,for the measurement of positive, negative and zero sequence components of a three phase system.
  
[List of Patents for class 324 subclass 87]    87
 This subclass is indented under subclass 83.  Subject matter having a lamp or space discharge device or nonlinear device.
(1) Note. The lamp and space discharge device of this subclass are of the type which are classified elsewhere (see the Search Notes below) The nonlinear device is one whose voltage-current relationship is significantly nonlinear, as, for example, a thermistor, contact rectifier, thyrite resistor, transistor, saturable reactor or nonlinear condenser.

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313Electric Lamp and Discharge Devices,   see the Class Definition of Class 313 for lamp and space discharge device of this subclass (324/87). See (1) Note above.
  
[List of Patents for class 324 subclass 88]    88
 This subclass is indented under subclass 87.  Subject matter having a cathode ray tube.
(1) Note. The cathode-ray tube usually serves as an indicator, but not necessarily so.

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313Electric Lamp and Discharge Devices,   subclasses 364+ , for cathode-ray tubes, per se.
315Electric Lamp and Discharge Devices: Systems,   subclasses 1+ for cathode-ray tube circuits of general application.
  
[List of Patents for class 324 subclass 89]    89
 This subclass is indented under subclass 87.  Subject matter having a space discharge device of the discharge control type.
(1) Note. The discharge may be controlled, for example, by means of a grid or by means of a magnetic field. The space discharge device may be of either the vacuum, gas or vapor type.
  
[List of Patents for class 324 subclass 90]    90
 This subclass is indented under subclass 83.  Subject matter having an indicating instrument of the type which has a stator element which produces a magnetic field by means of a supplied current.
(1) Note. The electrodynamometer instruments usually do not have a permanent magnetic field, but not necessarily so. They are, for example, of the ratio-meter type.

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144,for the electrodynamometer instrument, per se.
  
[List of Patents for class 324 subclass 91]    91
 This subclass is indented under subclass 83.  Subject matter for indicating if two voltages or currents are in phase.
(1) Note. The indication may be quantitative or qualitative, as, for example, "lead" and "lag". The measurement must be of a phase angle and not of some unrelated quantity. Thus, for example, a mere voltmeter, even though designated a "synchroscope", is not classified here but is classified with the appropriate art.

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84,through 90, for this subject matter where the synchroscope is of the type set forth in subclasses 84 through 90.
  
[List of Patents for class 324 subclass 92]    92
 This subclass is indented under subclass 76.  Subject matter having fluid means as a part thereof.
(1) Note. The fluid means must be significant to the electrical measurement or to the apparatus used in the measurement, and may be used, for example, as an expansible means in a thermal meter, as a lubricant, or as a cooling means.

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155,for meter pivots and bearings.

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73Measuring and Testing,   subclasses 861+ for fluid rate of flow or volume meters, 290+ for fluid depth gages, and 700+ for fluid pressure gages.
137Fluid Handling,   appropriate subclasses, for the subject matter of that class. Note subclasses 123+ for syphons, and subclasses 334+ for fluid handling with heating.
  
[List of Patents for class 324 subclass 93]    93
 This subclass is indented under subclass 92.  Subject matter in which the fluid is electrically conductive and having means to cause electricity to flow through the fluid.
(1) Note. The fluid is usually mercury, but may be any other conductive fluid, such as a molten alloy. Herein are found, inter alia, mercury type ampere hour meters.
  
[List of Patents for class 324 subclass 94]    94
 This subclass is indented under subclass 93.  Subject matter in which the fluid is electrolytic and having means to cause an electrolytic action to take place.

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205Electrolysis: Processes, Compositions Used Therein, and Methods of Preparing the Compositions,   appropriate subclasses for electrolysis utilized for electrochemistry and especially subclasses 775+ as the residual home for a process of electrolytic analysis or testing, per se.
252Compositions,   subclass 62.2 for electrolytes utilized in electrical devices, such as electrolytic condensers and rectifiers.
  
[List of Patents for class 324 subclass 95]    95
 This subclass is indented under subclass 76.  Subject matter having a wave guide or electrically long line.
(1) Note. A cavity resonator is a special case of a wave guide.

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94+,for similar subject matter utilized in electrical testing other than the measuring of electricity, per se.

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333Wave Transmission Lines and Networks,   subclasses 236+ , for long lines and wave guides, per se, and consult the class notes of Class 333 and the subclass definition notes for a definition of these terms.
  
[List of Patents for class 324 subclass 96]    96
 This subclass is indented under subclass 76.  Subject matter utilizing radiant energy means as a part thereof.
(1) Note. A voltage being measured may, for example, be applied to an electric light and the luminuous flux produced by the light may be taken as a measure of the voltage being measured.

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250Radiant Energy,   appropriate subclasses for the detections of nuclear or invisible radiant energy particularly subclasses 336.1+ for invisible radiant energy responsive electric signalling devices.
343Communications: Radio Wave Antennas,   subclass 703 for antenna combined with structure which tells the magnitude of the signal energy flowing in, to or from the antenna, a significant relationship existing between the antenna and the measuring structure.
356Optics: Measuring and Testing,   subclass 46 for incandescent standards, and subclasses 213+ for photometers.
  
[List of Patents for class 324 subclass 97]    97
 This subclass is indented under subclass 96.  Subject matter having means to direct the radiant energy in beams.
(1) Note. This subclass includes, for example, reflection galvanometers of the mirror type and pointer instruments having optical means to project an enlarged image of the pointer onto a scale.

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154,for rotors that are mounted on filar suspensions.
  
[List of Patents for class 324 subclass 98]    98
 This subclass is indented under subclass 76.  Subject matter having means for actively bringing a state of balance between mechanical or electrical forces into existence.
(1) Note. This subclass includes, for example, potentiometers in which the potential of an unknown voltage is balanced against the potential of a standard cell.
(2) Note. The mere passive balancing that occurs in an instrument such as the D"Arsonval meter, where the spring restoring torque equals the rotor torque, is not the type of balancing which is the subject matter of this subclass. But balancing without deflection, for example, is found here.
  
[List of Patents for class 324 subclass 99]    99
 This subclass is indented under subclass 98.  Subject matter having automatic means for bringing about the state of balance.

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318Electricity: Motive Power Systems,   subclasses 560+ , and the classes referred to in the search notes to these subclasses for follow-up electric motor systems, also known as rebalancing and servo motor systems.
330Amplifiers,   subclasses 144+ for amplifier systems including automatically variable impedance in the signal path.
  
[List of Patents for class 324 subclass 100]    100
 This subclass is indented under subclass 99.  Subject matter in which the result of the balancing operation is recorded.

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113,for similar subject matter not having automatic balancing means.

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346Recorders,   subclass 31 and 32 for this subject matter.
  
[List of Patents for class 324 subclass 101]    101
 This subclass is indented under subclass 76.  Subject matter having a Wheatstone bridge and having means to indicate the current which results because of the unbalance.

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57+,for Wheatstone bridges used to measure impedance.
98+,for this subject matter having a Wheatstone bridge which is balanced.

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323Electricity: Power Supply or Regulation Systems,   subclass 365 , for miscellaneous Wheatsone bridge circuits and consult the search notes to that subclass for a list of the other classes which have provision for Wheatstone bridges.
330Amplifiers,   subclasses 72 , 146 and 175, for amplifier systems wherein series arranged vacuum tubes are in the arms of a bridge, wherein at least one arm of a Wheatstone bridge, and wherein there is a Wheatstone bridge in the signal coupling circuit, respectively.
  
[List of Patents for class 324 subclass 102]    102
 This subclass is indented under subclass 76.  Subject matter which is responsive to a transient or which is used to determine some characteristic of a transient or some characteristic of a portion of a wave form of a cyclic wave.
(1) Note. This subclass includes, for example, the determination of the complete wave form of a transient, such as results when a short circuit occurs on a transmission line.

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100,and 113, for recorders which are equally responsive to transients and steady state voltages.
103+,for peak voltmeters or maximum current ammeters.
121,for cathode ray oscilloscopes which are equally responsive to steady state and transient voltages.
  
[List of Patents for class 324 subclass 103]    103
 This subclass is indented under subclass 76.  Subject matter having means for indicating the demand for electricity, averaged over a set period of time, or having means for indicating the consumption of electricity exceeding a set minimum or having means for indicating the maximum or minimum value of the electricity.
(1) Note. The demand may be indicated in various manners, as by average demand over a period of time larger than the set period of time, maximum demand, integrated demand, or otherwise, and may be expressed in terms of watts, voltamperes or otherwise. The excess consumption may likewise be expressed in various manners, such as integrated excess or excess demand.

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102,for the measurement of some characteristic of a transient, other than mere maximum or minimum.
116,for multi-rate registering meters which register at different rates depending upon demand.
139,for time controlled meters which do not measure demand.
  
[List of Patents for class 324 subclass 104]    104
 This subclass is indented under subclass 103.  Subject matter having means whose temperature is varied in accordance with the electricity being measured and having means, responsive to said temperature variation for indicating the demand, excess consumption, maximum, or minimum.

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92,for this subject matter having fluid means, such as thermal expansion meters.
  
[List of Patents for class 324 subclass 105]    105
 This subclass is indented under subclass 76.  Subject matter having means which are significant because of some thermal relationship.
(1) Note. This subclass includes, for example, cooling features and means for compensating an instrument for changes in the ambient temperature. Thermally actuated meters are in indented subclass 106.
  
[List of Patents for class 324 subclass 106]    106
 This subclass is indented under subclass 105.  Subject matter having means whose temperature is varied in accordance with the electricity being measured and having means, responsive to said temperature variation, for indicating the result of the measurement.
(1) Note. This subclass includes, for example, hot wire ammeters of both the expansion or bimetallic type and the thermocouple type.

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92,for this subject matter having fluid means, such as thermal fluid expansion meters.
104,for this subject matter for indicating demand, excess, maximum or minimum.

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374Thermal Measuring and Testing,   subclasses 100+ , for thermometers, per se.
  
[List of Patents for class 324 subclass 107]    107
 This subclass is indented under subclass 76.  Subject matter responsive to the voltages or currents in a polyphase system.
(1) Note. A polyphase system is a group of alternating current circuits, usually interconnected, which enter or leave a region at more than two points of entry or exit, and which are so energized that in the steady state the alternating currents through the point of entry or exit and the alternating potential differences between them all have substantially equal periods, but have differences in phase and may have differences in wave form.

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140+,for single phase systems of the three wire type, having means to measure the energy in such systems. Note that some of such metering systems are inherently capable of also measuring polyphase energy. Also consult the search notes to subclass 140.
  
[List of Patents for class 324 subclass 108]    108
 This subclass is indented under subclass 107.  Subject matter for measuring the positive, negative or zero sequence of current of voltage in the polyphase system or responsive to one of these factors.
  
[List of Patents for class 324 subclass 109]    109
 This subclass is indented under subclass 76.  Subject matter having means for utilizing electrostatic attraction or repulsion or piezo-electric action in order to respond to the electricity.

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78+,and 83+, for this subject matter when utilized to measure frequency or compare phase as, for example, in synchroscopes.

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310Electrical Generator or Motor Structure,   subclass 309 for electrostatic motors and subclasses 311+ for piezo-electric devices and systems, per se.
361Electricity: Electrical Systems and Devices,   subclasses 271+ for electrostatic condensers, per se.
  
[List of Patents for class 324 subclass 110]    110
 This subclass is indented under subclass 76.  Subject matter for protecting the electric measuring apparatus or for combating attempts to cause the meter to read inaccurately.
(1) Note. This subclass includes, for example, meters combined with fuses to protect the meter against accidental overloads and meters that are provided with special circuit means to cause the meter to continue to register if the potential coil is disconnected by a customer of a utility company who is attempting to defraud the company.

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156,for meters having casings which serve to protect the meter mechanically.

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361Electricity: Electrical Systems and Devices,   subclasses 659+ for meters having casings and similar structures to protect the meters mechanically.
  
[List of Patents for class 324 subclass 111]    111
 This subclass is indented under subclass 76.  Subject matter having means to store the electricity which is being measured.
(1) Note. This subclass relates to storage means, such as condenser banks, which store the electricity in such a manner that the original wave form can be recovered, and also relates to condensers which are used to integrate the electricity.

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178Telegraphy,   subclass 17.5 , for telegraph systems having storage means for temporarily holding signals.
315Electric Lamp and Discharge Devices: Systems,   subclasses 8.51+ for cathode ray tube systems for accumulating or storing electrical pulse energy for later retrieval, and subclasses 84.51+ for similar electrical pulse storage systems utilizing electric space discharge devices of the gaseous type.
365Static Information Storage and Retrieval,   appropriate subclass for the storage and retrieval of information. This class excludes the mere storage of control signals.
  
[List of Patents for class 324 subclass 112]    112
 This subclass is indented under subclass 111.  Subject matter in which the electricity is stored in an extended tape or wire or in a sheet medium.
(1) Note. This subclass relates to, for example, the storage of the electricity in a disk, similar to a phonograph record, and to the storage of the electricity in magnetic wire or tape.

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360Dynamic Magnetic Information Storage or Retrieval,   for magnetic recording or reproducing.
365Static Information Storage and Retrieval,   appropriate subclass for the storage and retrieval of information. This class excludes the mere storage of control signals.
369Dynamic Information Storage or Retrieval,   for dynamic storage of information signals.
  
[List of Patents for class 324 subclass 113]    113
 This subclass is indented under subclass 76.  Subject matter for recording the result of the measurement of the electricity.
(1) Note. Many of the Classes have provision for their own recording systems, consequently, in appropriate instances, the search for a recorder should extend to the class relating to the environment in which the recorder might be found.

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346Recorders,   appropriate subclasses, for this same subject matter. In Class 346 there is no subclass which relates specifically to the recording of electricity, per se, but the recorders are classified on the basis of the manner in which the record is made. Note subclass 150.2 in which an electric spark is utilized to mark a phenomenal record.
347Incremental Printing of Symbolic Information,   subclasses 111+ for electric recorders comprising means for applying electricity to a medium for recording an image.
  
[List of Patents for class 324 subclass 114]    114
 This subclass is indented under subclass 76.  Subject matter having plural meters.
(1) Note. The meters may be of the same or of different kinds and may be separated or may be combined to one case.

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115,for single meters which have plural ranges or plural scales.

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340Communications: Electrical,   subclasses 870.41 and 870.15 for telemetering systems having plural receivers or meters.
361Electricity: Electrical Systems and Devices,   subclass 660 for switchboards having plural meters.
  
[List of Patents for class 324 subclass 115]    115
 This subclass is indented under subclass 76.  Subject matter having plural ranges, plural scales, or plural registration rates.

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114,for meters having plural scales or plural ranges where both scales or both ranges are simultaneously usable, (i.e., where there are plural meters).
  
[List of Patents for class 324 subclass 116]    116
 This subclass is indented under subclass 115.  Subject matter having a register.
(1) Note. This subclass includes, for example, watt hour meters which register at one rate for an initial period and then register at a different rate for other periods.

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103,for demand meters, per se, i.e., meters that indicate purely demand and not some quantity of which demand is but a factor.
139,for time controlled meters of the registering type which do not register at plural rates.
  
[List of Patents for class 324 subclass 117]    117
 This subclass is indented under subclass 76.  Subject matter having magnetic means in which a significant amount of saturation occurs during the operation thereof.
(1) Note. This subclass relates, for example, to metering systems having magnetic amplifiers and to meters having saturated pole tips.

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323Electricity: Power Supply or Regulation Systems,   subclasses 249 , 302, 310, and 329, for magnetic amplifiers of the nonlinear type.
330Amplifiers,   subclass 10 for amplifier systems wherein the active element is a saturable core reactor.
  
[List of Patents for class 324 subclass 118]    118
 This subclass is indented under subclass 76.  Subject matter having means to modulate the voltage or current being measured onto a carrier wave and having further means to demodulate the resulting modulating carrier wave into a replica of the original voltage or current.
(1) Note. This subclass relates, for example, to direct current voltmeters which measure a very small direct current voltage which small voltage is amplified in the modulator-demodulator apparatus so that it is large enough to actuate a conventional meter.

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329Demodulators,   appropriate subclasses for demodulators, per se.
330Amplifiers,   subclass 10 for modulator-demodulator amplifiers, per se.
332Modulators,   appropriate subclasses, for modulators.
  
[List of Patents for class 324 subclass 119]    119
 This subclass is indented under subclass 76.  Subject matter having a rectifier.
(1) Note. The rectifier may be used, for example, to change an alternating current input into a direct current output, or the rectifier may be used merely as a nonlinear element.

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363Electric Power Conversion Systems,   appropriate subclasses for miscellaneous rectifying systems.
  
[List of Patents for class 324 subclass 120]    120
 This subclass is indented under subclass 76.  Subject matter having means to transform the voltage or current to be measured into a different current or voltage and having means to measure said different voltage or current.
(1) Note. This subclass contains, for example, systems where a DC voltage is changed into an AC voltage which is measured as an AC voltage, systems wherein the input voltage is converted into a pulse voltage and systems wherein the input voltage is converted from one frequency into another frequency.

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118,for this subject matter wherein the input voltage or current is first modulated and then demodulated.
119,for this subject matter having a rectifier.

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340Communications: Electrical,   subclasses 870.01+ for telemetering systems having no significant measuring, testing or sensing of the condition to be telemetered. Some telemetering systems utilize current conversion means. Note indented subclasses 870.19+ for telemetering systems in which the value of the condition is represented by a pulse code.
  
[List of Patents for class 324 subclass 121]    121
 This subclass is indented under subclass 76.  Subject matter having a cathode-ray tube.
(1) Note. The cathode-ray tube may be an indicator as, for example, a cathode ray oscilloscope or a "magic eye" tube, or the cathode-ray tube may be a control tube of some type.

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88,for this subject matter utilized to measure phase displacement between two voltages.

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313Electric Lamp and Discharge Devices,   subclasses 364+ , for cathode-ray tubes, per se.
315Electric Lamp and Discharge Devices: Systems,   subclasses 1+ , for cathode- ray tubes circuits of general application. Note that Class 315 includes, among its cathode-ray tube systems, those systems in which an unknown voltage is applied to the deflecting means of the cathode-ray tube so that the unknown voltage may be observed. The system is not excluded from Class 315 unless some means is claimed to enable the desired information to be derived other than merely observing the trace of the ray on an unchartered luminous screen.
  
[List of Patents for class 324 subclass 122]    122
 This subclass is indented under subclass 76.  Subject matter having a gaseous discharge device.
(1) Note. A gaseous discharge device is defined as being a device having two spaced electrodes between which electricity flows and having either gas or vapor in the space between the electrodes.
(2) Note. This subclass includes, for example, spark gap volt meters and metering systems using a gaseous discharge device as a nonlinear impedance.

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313Electric Lamp and Discharge Devices,   subclasses 567+ for gaseous discharge devices, per se.
315Electric Lamp and Discharge Devices: Systems,   appropriate subclasses for miscellaneous gas discharge device systems.
  
[List of Patents for class 324 subclass 123]    123
 This subclass is indented under subclass 76.  Subject matter having an amplifier or having a space discharge device.

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117,for this subject matter utilizing magnetic saturation type amplifiers.
121,for this subject matter when the space discharge device is a cathode-ray tube.
122,for this subject matter when the space discharge device is a gaseous discharge device.

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330Amplifiers,   for amplifiers, per se.
  
[List of Patents for class 324 subclass 124]    124
 This subclass is indented under subclass 123.  Subject matter having an inverted amplifier.
(1) Note. An inverted amplifier is defined as one having an amplification factor which is less than unity. Usually this is achieved by connecting the input circuit to the plate of a vacuum tube and taking the output from the grid of a vacuum tube. The inverted amplifier acts as an attenuating circuit to couple the meter to the source of voltage or current being measured.

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330Amplifiers,   subclass 250 for inverted transistor amplifiers, and subclasses 160+ and 162+ for inverted amplifiers of the vacuum tube type.
  
[List of Patents for class 324 subclass 125]    125
 This subclass is indented under subclass 76.  Subject matter having means to control the mechanical vibrations which result because of inertia, elasticity, and damping or having means to control vibrations which arise outside or inside the measuring means.
(1) Note. This subclass includes, for example, instruments having "dead beat" characteristics.

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123,for this subject matter having amplifier means with negative feed back control, for the purpose of controlling the inertia effects.

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73Measuring and Testing,   subclass 430 for instrument mechanism dampening, per se, subclasses 514.12+ for fluid or fluent material dampening of an inertial member in an acceleration measuring apparatus, and subclass 514.14 for vibration dampening in an inertial-type acceleration measuring apparatus.
248Supports,   subclasses 560+ for resilient supports.
  
[List of Patents for class 324 subclass 126]    126
 This subclass is indented under subclass 76.  Subject matter having means for coupling the measuring device to the source of current or voltage being measured.
(1) Note. Such means, for example, may be an attenuator or an instrument shunt.

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115,for this subject matter in instruments having plural ranges.
149,for measuring instruments having mere prods, probes or other terminal structure without circuit elements other than conductors.

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333Wave Transmission Lines and Networks,   subclasses 24+ for coupling networks, per se.
338Electrical Resistors,   subclass 49 for electrical resistors of the shunt type.
  
[List of Patents for class 324 subclass 127]    127
 This subclass is indented under subclass 126.  Subject matter in which the coupling means is a transformer.
(1) Note. The transformer, for example, may be of the type having a core which can be opened to admit a current carrying conductor.

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129,for instruments having pole pieces which will admit a nonunitary input conductor without disconnecting or cutting said implement conductor.

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336Inductor Devices,   appropriate subclasses for the structure of transformers, per se. Of special interest are subclass 172 , for "Fractional turn" type inductive devices (including transformers), and subclasses 173+ and 175+ which include current transformers.
  
[List of Patents for class 324 subclass 128]    128
 This subclass is indented under subclass 126.  Subject matter in which the coupling means is a selective filter.
(1) Note. The filter may be a high pass, low pass or band pass filter.

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333Wave Transmission Lines and Networks,   subclasses 167+ , for wave filters, per se.
  
[List of Patents for class 324 subclass 129]    129
 This subclass is indented under subclass 76.  Subject matter having pole piece means so constructed that they will admit an input conductor without cutting or disconnecting said conductor.
(1) Note. This subclass includes, for example, "hook on" ammeters of the type not equipped with an integral transformer.

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127,for similar subject matter utilizing a transformer of the split core type.
  
[List of Patents for class 324 subclass 130]    130
 This subclass is indented under subclass 76.  Subject matter having means for self-calibrating the instrument.

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74+,for calibrating means for electric instruments, per se.
  
[List of Patents for class 324 subclass 131]    131
 This subclass is indented under subclass 76.  Subject matter in which the measuring instrument indications are of the suppressed zero type.
(1) Note. Suppressed zero refers to that condition of instrument in which the scale reading does not extend from zero to an upper value but rather from an intermediate value to an upper value.
  
[List of Patents for class 324 subclass 132]    132
 This subclass is indented under subclass 76.  Subject matter in which the measuring instrument indications are of the nonlinear type.
(1) Note. The instrument deflection, for example, may be related to the input current or voltage in a logarithmic manner.
  
[List of Patents for class 324 subclass 133]    133
 This subclass is indented under subclass 76.  Subject matter for giving a nonquantitative indication.
(1) Note. This subclass includes, for example, polarity testers and "hot-line" indicators.
(2) Note. A quantitative instrument may be modified into a nonquantitative instrument by merely omitting the scale. Consequently, in appropriate instances, the search should extend to the pertinent quantitative type subclass.

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340Communications: Electrical,   appropriate subclasses for similar subject matter. Also see the search note to Class 340 in the class definition of this class (324).
362Illumination,   appropriate subclasses, for electric lamp luminaries, many of which could be used as nonquantitative indicators.
  
[List of Patents for class 324 subclass 134]    134
 This subclass is indented under subclass 76.  Subject matter having a commutator or having a reversing switch or having a pulsating switch.
(1) Note. This subclass includes, for example, DC watt hour meters.

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200Electricity: Circuit Makers and Breakers,   appropriate subclasses for the structure of switches, per se.
310Electric Generator or Motor Structure,   appropriate subclasses, for motors having commutators.
361Electricity: Electrical Systems and Devices,   subclasses 139+ for relay systems, per se.
  
[List of Patents for class 324 subclass 135]    135
 This subclass is indented under subclass 134.  Subject matter having a rotor which oscillates between two positions.

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73Measuring and Testing,   subclass 430 for instrument mechanism dampening, per se, subclasses 514.12+ for fluid or fluent material dampening of an inertial member in an acceleration measuring apparatus, and subclass 514.14 for vibration dampening in an inertial-type acceleration measuring apparatus.
310Electrical Generator or Motor Structure,   subclasses 36+ for oscillating motors, per se.
  
[List of Patents for class 324 subclass 136]    136
 This subclass is indented under subclass 76.  Subject matter having a rolling ball or a rolling wheel.
(1) Note. The ball or wheel are usually part of an integrating mechanism, but may be part of a speed transmission.

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33Geometrical Instruments,   subclass 121 for area integrators, per se.
235Registers,   appropriate subclasses, particularly subclasses 65 , 66 and 68, for calculating devices and machines having integrating features.
  
[List of Patents for class 324 subclass 137]    137
 This subclass is indented under subclass 76.  Subject matter having a rotor upon which torque is exerted by means of an electo-magnetic field which produces eddy current in the rotor.
(1) Note. This subclass includes, for example, the familiar AC integrating watt hour meter. The rotor is often known as a Ferraris disk.
(2) Note. The rotor in this subclass may rotate continuously or may rotate through only a certain angle as determined by the stiffness of a spring which restrains further rotation.

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152,for this subject matter where the eddy current rotor is merely a drag disk.

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310Electrical Generator or Motor Structure,   subclasses 166+ for eddy current motors of general application.
318Electricity: Motive Power Systems,   subclasses 727+ for eddy current motor systems of general application. Note particularly indented subclasses 781+, for eddy current motors which operate from a single phase source.
  
[List of Patents for class 324 subclass 138]    138
 This subclass is indented under subclass 137.  Subject matter having means to vary the time-phase relationship between two alternating magnetic fields.
(1) Note. The time-phase relationship, for example, may be adjusted so as to bring the alternating magnetic fields into time quadrature, or it may be adjusted so that they are slightly out of quadrature.

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148,for other measuring means having phase shift means.

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318Electricity: Motive Power Systems,   subclass 729 for power-factor control of induction motor systems including eddy current motor systems.
323Electricity: Power Supply or Regulation Systems,   subclasses 212 through 219for phase shifting means, per se.
  
[List of Patents for class 324 subclass 139]    139
 This subclass is indented under subclass 76.  Subject matter having rotary motor driving means which rotate constantly, independently of the electricity being measured, or having time control means or having means which oscillate.
(1) Note. Time control means may be, for example, a clock which rotates at a constant speed or an electric synchronous motor which rotates at a constant speed. Oscillating means may be means such as an anchor escapement or a stepping ratchet.
(2) Note. This subclass relates, for example, to integrating meters wherein an element periodically oscillates at an amplitude which is determined by the quantity to be integrated (variable stroke) or at a radius which is determined by that quantity (variable radius).

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103+,for demand, excess, maximum or minimum meters which provide a final indication of which time is but a factor.
116,for multi-rate registering meters which register at different rates in accordance with a function of time.
135,for oscillating measuring means in which a pulsating or reversing switch is associated with the oscillating means.
136,for variable radius type meters which utilize a rolling ball or wheel.

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74Machine Element or Mechanism,   appropriate subclasses, for ratchet mechanisms.
368Horology: Time Measuring Systems or Devices,   for clocks and watches. Note subclasses 155+ , for those having electrical features.
  
[List of Patents for class 324 subclass 140]    140
 This subclass is indented under subclass 76.  Subject matter having plural inputs to the measuring means.
(1) Note. A single circuit can furnish plural inputs to the measuring means, since a single circuit can carry a voltage and a current independently of each other. Thus, the indented subclasses contain watt meters and volt-ampere meters of the type which are not found in subclasses above.
(2) Note. This subclass includes, for example, ratio meters and summation meters.

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62+,for complete resistance measuring systems including, as a part thereof, ratio meters.

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340Communications: Electrical,   subclasses 870.01+ for telemetering systems for indicating at a remote point the value of a local condition. Note subclasses 870.11+ where the condition at plural localities is sensed. Note subclasses 870.19+ where the value of the condition is coded into a pulse type code.
  
[List of Patents for class 324 subclass 141]    141
 This subclass is indented under subclass 140.  Subject matter for measuring volt amperes.
(1) Note. The volt amperes may be either real or reactive. Reactive volt amperes are often referred to as volt vars,

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137+,for this subject matter having an eddy current rotor.
  
[List of Patents for class 324 subclass 142]    142
 This subclass is indented under subclass 140.  Subject matter for measuring watts.
(1) Note. This subclass contains, for example, watt meters of the dynamometer type.

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134,for this subject matter having a commutator or a reversing or pulsating switch.
137+,for this subject matter having an eddy current rotor.
  
[List of Patents for class 324 subclass 143]    143
 This subclass is indented under subclass 76.  Subject matter having plural active motor elements.
(1) Note. The plural active motor element may be mounted on a single shaft to operate a single indicator, or they may be mounted on two shafts to operate two rotary arms whose variable point of intersection determines the final indication.

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114,for plural meters.
115,for a single meter having plural ranges or scales.
  
[List of Patents for class 324 subclass 144]    144
 This subclass is indented under subclass 76.  Subject matter having a stationary means to produce a magnetic field by the flow of electricity through a winding.
(1) Note. This subclass includes, for example, electrodynamometer type instruments having only a single input.

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134+,for this subject matter having a rotor with a commutator or reversing or pulsating switch.
137+,for this subject matter having an eddy current rotor.
140+,for this subject matter having plural inputs.

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310Electrical Generator or Motor Structure,   subclasses 10+ , for dynamo electric structure of general application.
  
[List of Patents for class 324 subclass 145]    145
 This subclass is indented under subclass 144.  Subject matter having a core armature which is attracted by the magnetic field and which moves, under said attraction, along its own axis.

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335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 255+ for plunger type solenoids, per se.
  
[List of Patents for class 324 subclass 146]    146
 This subclass is indented under subclass 144.  Subject matter having a permanent magnet.
(1) Note. The permanent magnet may supplement the magnetic field produced by the electromagnet or it may be acted upon by the electromagnetic field.

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147,for similar subject matter having soft instead of hard iron.

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335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 299+ for similar subject matter, not restricted to the measurement of electricity.
  
[List of Patents for class 324 subclass 147]    147
 This subclass is indented under subclass 144.  Subject matter having an iron rotor.

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146,for this subject matter where the iron rotor is or becomes a permanent magnet under any conditions of operation.
  
[List of Patents for class 324 subclass 149]    149
 This subclass is indented under subclass 76.  Subject matter having a probe, a prod or a specific terminal.

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72.5,for similar subject matter in combination with a high frequency testing device.
119,for this subject matter having a rectifier in the probe.

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361Electricity: Electrical Systems and Devices,   subclass 668 for meter terminal or connector arrangements.
439Electrical Connectors,   appropriate subclasses for an electrical terminal, per se.
  
[List of Patents for class 324 subclass 150]    150
 This subclass is indented under subclass 76.  Subject matter having a rotor which has a coil which is eccentrically mounted with respect to the axis of the rotor.
(1) Note. The coil, for example, may be of rectangular shape and the axis of the rotor may correspond with one of the sides of the rectangle.

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140,for this subject matter having plural inputs, as in ratio-meters.
  
[List of Patents for class 324 subclass 151]    151
 This subclass is indented under subclass 76.  Subject matter having a permanent magnet.
(1) Note. This subclass relates, for example, to D"Arsonval type instruments and to magnetic suspensions for instrument rotors.

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146,for this subject matter also having a magnetic field produced by an electromagnet.
171+,for similar subject matter not restricted to the measurement of electricity.

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310Electrical Generator or Motor Structure,   subclass 90.5 for a bearing having a magnetic suspension.
335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 302+ for permanent magnets, per se.
  
[List of Patents for class 324 subclass 152]    152
 This subclass is indented under subclass 151.  Subject matter in which the permanent magnet is associated with an eddy current means and the permanent magnet acts as a drag for the eddy current means.
(1) Note. The eddy current means usually is a disk rotor.

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103,for excess type meters which utilize a hysteresis type brake (which has a constant counter-torque at all speeds) having a permanent magnet and for meters in which the torque on the drag magnet actuates an indicator by movement of the drag magnet.
137+,for similar subject matter where an eddy current disk acts both as a motive element and a drag element.
139,for meters having a rotor which is driven by a constant torque device and having a brake whose drag is determined by the electricity to be measured.

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310Electrical Generator or Motor Structure,   subclasses 103+ , for magnetic field type torque transmitting brakes and clutches.
  
[List of Patents for class 324 subclass 153]    153
 This subclass is indented under subclass 76.  Subject matter having a register.
(1) Note. A registering means is herein defined as being a device which converts a linear or rotational movement into a number which corresponds to the movement and is a measure thereof. Generally the register is provided with means for separately indicating the value of the several digits which go to make up the number that is a measure of the indication.
  
[List of Patents for class 324 subclass 154]    154
 This subclass is indented under subclass 76.  Subject matter having a rotor.
(1) Note. This subclass includes, for example, rotors provided with filar suspensions, rotors having means for setting them to zero, and rotors having means to balance them.
  
[List of Patents for class 324 subclass 155]    155
 This subclass is indented under subclass 154.  Subject matter having significant bearing or pivot structure.
(1) Note. A bearing or pivot is significant when it is claimed by more than name only or when it is disclosed as being significant.

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151,for magnetic suspensions which decrease friction by decreasing bearing load.
403+,for meters with fluid means, such as lubricating means.

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310Electrical Generator or Motor Structure,   subclass 90.5 for a bearing having a magnetic suspension.
  
[List of Patents for class 324 subclass 156]    156
 This subclass is indented under subclass 76.  Subject matter having a casing for the instrument.

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73Measuring and Testing,   subclass 431 , for this subject matter.
312Supports: Cabinet Structure,   for miscellaneous casings.
361Electricity: Electrical Systems and Devices,   subclasses 659+ for special meter casings, and subclasses 664+ for meter mounting arrangements.
  
[List of Patents for class 324 subclass 157]    157
 This subclass is indented under subclass 76.  Subject matter combined with some other type of subject matter.
(1) Note. The meter, for example, may be combined with a specific type of distribution system.
(2) Note. A meter in a specific environment, generally, but not invariably, is classified with the specific environment. Consequently, in appropriate instances, the search should extend to the class which relates to the environment.

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72,for the measurement of electricity in a specific environment.
116,for multi-rate registering meters which may, for example, be combined with two load circuits having loads of different tariff rates.

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307Electrical Transmission or Interconnection Systems,   appropriate subclasses for systems for distributing electricity.
  
[List of Patents for class 324 subclass 160]    160
 This subclass is indented under the class definition.  Subject matter wherein are provided processes or means to produce an electrical signal representative of the time rate of change of position (speed) of a physical element and to indicate, in response to said signal, said time rate.

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73Measuring and Testing,   subclasses 178+ , for navigational speed measuring devices such as ship’s logs, leeway incidence or rate of climb; subclasses 861+, for volume or rate of flow meters; subclasses 488+, for mechanical speed measuring devices and indented subclasses 519.01+, for permanent magnet type speedometers.
340Communications: Electrical,   subclasses 441 and 446, for vehicle speed actuated signals and subclasses 670+, for speed actuated signals and alarms in general.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 104+ for radar type systems which determine the velocity of an object.
346Recorders,   subclass 18 , for recorders combined with a speed indicator or alarm.
356Optics: Measuring and Testing,   subclasses 27+ , for velocity or velocity/height measuring systems including optical sighting systems.
361Electricity: Electrical Systems and Devices,   subclass 51 and subclasses 236+ for control systems responsive to speed.
700Data Processing: Generic Control Systems or Specific Applications,   subclass 304 for speed control.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 141 and 142+ for acceleration and speed measuring systems, respectively.
  
[List of Patents for class 324 subclass 161]    161
 This subclass is indented under subclass 160.  Subject matter in which means are provided for comparing one speed signal with another speed signal or a reference signal.
(1) Note. The comparison means is not necessarily electrical.

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79,for comparison of the frequencies of two electrical signals.

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307Electrical Transmission or Interconnection Systems,   subclass 123 , for switching systems responsive to the differential speed between two bodies.
361Electricity: Electrical Systems and Devices,   subclasses 243+ for the synchronization of rotating shafts which requires a comparison of the speeds of the shafts. Also consult the search notes to that subclass for a compilation of other pertinent classes.
  
[List of Patents for class 324 subclass 162]    162
 This subclass is indented under subclass 160.  Subject matter including means producing an electrical signal representative of the time rate of change of speed or a physical object.
(1) Note. This subclass relates to electrical accelerometers other than, for example, those which sense acceleration by means of an inertial element.
(2) Note. The means of this subclass may include means responsive to acceleration, per se, or means responsive to a speed signal to derive the acceleration.

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73Measuring and Testing,   subclasses 514.01+ , for means indicating acceleration including an inertial element. See (1) Note above.
307Electrical Transmission or Interconnection Systems,   subclass 121 , for switching systems responsive to acceleration.
340Communications: Electrical,   subclass 669 , for acceleration or deceleration responsive signals or alarms.
700Data Processing: Generic Control Systems or Specific Applications,   subclass 304 for speed control.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 141 and 142+ for acceleration and speed measuring system, respectively.
  
[List of Patents for class 324 subclass 163]    163
 This subclass is indented under subclass 160.  Subject matter in which means for producing a signal representative of speed includes means to convert mechanical motion into an electrical signal whose output amplitude is a function of the speed being measured, and in which the indicating means measures said amplitude.

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166+,for electrical generators of speed signals whose frequency is a function of the speed being measured.

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310Electrical Generator or Motor Structure,   subclasses 10+ , for dynamoelectric generator structure.
322Electricity: Single Generator Systems,   appropriate subclasses, for single dynamoelectric generator systems.
  
[List of Patents for class 324 subclass 164]    164
 This subclass is indented under subclass 163.  Subject matter in which the electrical generator includes a conductive, nonferromagnetic armature whose movement is representative of the speed being measured, means to induce an electric current in said armature and means responsive to the current to indicate the speed of the armature.

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310Electrical Generator or Motor Structure,   subclass 171 , for induction generator structure.
322Electricity: Single Generator Systems,   subclass 47 , for induction generator systems.
  
[List of Patents for class 324 subclass 165]    165
 This subclass is indented under subclass 163.  Subject matter combined with means to indicate the sense of motion (e.g., forward or backward, clockwise or counter clockwise) within a given path, of the object whose speed is being measured.

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33Geometrical Instruments,   subclass 204 , for direction indicators in general which are responsive to some force.
116Signals and Indicators,   subclasses 200+ , for mechanically actuated shaft rotation indicators.
307Electrical Transmission or Interconnection Systems,   subclass 122 , for switching systems responsive to direction of rotation.
340Communications: Electrical,   subclass 465 , for signal means for automatically indicating the direction of movement of a vehicle, and subclasses 671+, for signal means for indicating machine shaft rotation or direction.
  
[List of Patents for class 324 subclass 166]    166
 This subclass is indented under subclass 160.  Subject matter in which the signal producing means produces a periodic electrical signal whose frequency is a function of the speed being measured.
(1) Note. This subclass includes, for example, apparatus in which an electrical pulse is produced each time the moving object traverses a fixed increment of distance. The movement thus sensed may be either linear or angular (e.g., rotary).

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78+,for the measurement of the frequency of cyclic electric currents of voltages.
  
[List of Patents for class 324 subclass 167]    167
 This subclass is indented under subclass 166.  Subject matter including electro-magnetic, indicator driving means energized by the speed signal to produce a rotating magnetic field whose rotation is synchronized with the frequency of the speed signal.
(1) Note. The rotating magnetic field may drive freely rotating armature or a restrained armature either of which is, in turn, connected to some means to indicate the speed of the rotating field and, thus, the object whose speed is being measured.
  
[List of Patents for class 324 subclass 168]    168
 This subclass is indented under subclass 166.  Subject matter in which the means for producing a signal includes an electrical circuit breaker actuated at a frequency representative of the speed being measured.

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200Electricity: Circuit Makers and Breakers,   subclasses 19.01+ , for periodically actuated switches.
  
[List of Patents for class 324 subclass 169]    169
 This subclass is indented under subclass 168.  Subject matter in which the switch is also a component of an internal combustion engine ignition system.
  
[List of Patents for class 324 subclass 170]    170
 This subclass is indented under subclass 169.  Subject matter wherein the speed measuring means is connected to the secondary circuit of the ignition system; the voltage fluctuations of the secondary circuit thereby producing the speed signal.
  
[List of Patents for class 324 subclass 171]    171
 This subclass is indented under subclass 168.  Subject matter combined with means to indicate the distance the object whose speed is being measured has traveled during the speed measuring interval.
(1) Note. This subclass includes revolution counters as well as odometers.

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73Measuring and Testing,   subclass 490 , for mechanical speed and distance measuring systems.
  
[List of Patents for class 324 subclass 172]    172
 This subclass is indented under subclass 166.  Subject matter in which means for producing a speed signal includes a recording medium and means to move it at a speed proportional to speed being measured.
  
[List of Patents for class 324 subclass 173]    173
 This subclass is indented under subclass 166.  Subject matter in which the means for producing a speed signal included means producing a magnetic field and further means sensitive to changes in the field to produce an electrical signal.

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200,for magnetic detectors and systems therefor.

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73Measuring and Testing,   subclass 519.01 for a speed measuring device using a magnetic drag cup.
310Electrical Generator or Motor Structure,   subclasses 40+ , for rotary dynamoelectric generator structure.
322Electricity: Single Generator Systems,   appropriate subclasses for single dynamoelectric generator systems.
  
[List of Patents for class 324 subclass 174]    174
 This subclass is indented under subclass 173.  Subject matter in which the means for producing a magnetic field includes a permanent magnet.

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310Electrical Generator or Motor Structure,   subclasses 152+ for rotary, dynamoelectric generator structure including permanent magnets.
322Electricity: Single Generator Systems,   subclass 46 , for single dynamoelectric permanent-magnet generator systems.
  
[List of Patents for class 324 subclass 175]    175
 This subclass is indented under subclass 166.  Subject matter in which means for producing a speed signal includes means responsive to radiant energy (i.e., electromagnetic or atomic radiation) to produce or alter an electric current.
  
[List of Patents for class 324 subclass 176]    176
 This subclass is indented under subclass 160.  Subject matter in which the means for producing the electric speed signal includes a variable circuit element whose impedance varies as a function of the position of the object in the path along which its speed is being measured.
(1) Note. The impedance of the circuit element of this subclass being a function of displacement, the current through the element may, for example, be differentiated with respect to time to produce the speed signal.

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178,and the subclasses indented thereunder for systems including an element whose electrical characteristics change in response to the passage of an object.

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73Measuring and Testing,   subclasses 514.39+ , for apparatus including a mechanical speed indicating device with electrical means for sensing its indication, for example, a flyball governor with electrical means for sensing the radial displacement of the flyball.
  
[List of Patents for class 324 subclass 177]    177
 This subclass is indented under subclass 160.  Subject matter in which the means producing an electric speed signal is responsive to the supply voltage or current of an electric motor.

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318Electricity: Motive Power Systems,   and subclass 490 , for electric motors with signals, meters, recorders or testing devices.
388Electricity: Motor Control Systems,   appropriate subclasses, together with art collection 928.1, for running-speed and acceleration control systems for responsive to terminal electromotive force.
  
[List of Patents for class 324 subclass 178]    178
 This subclass is indented under subclass 160.  Subject matter wherein the means for producing a speed signal includes means responsive to the passage (event) of an object past a plurality spaced locations.
(1) Note. This subclass includes, for example, systems for measuring the time taken by an object such as projectile or vehicle to move through a measured distance. The "event" being the passage of the object past the ends of the measured distance.

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181+,for systems for measuring the duration of time intervals.

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73Measuring and Testing,   subclass 167 , for apparatus for testing ordinance and projectiles.
346Recorders,   subclass 38 , for recorders actuated responsive to ordinance.
  
[List of Patents for class 324 subclass 179]    179
 This subclass is indented under subclass 178.  Subject matter in which the means responsive to the passage of an object is sensitive to magnetic field variations caused by passage of the object through magnetic field.
  
[List of Patents for class 324 subclass 180]    180
 This subclass is indented under subclass 178.  Subject matter in which the means responsive to the passage of an object includes an electrical switch actuated directly by the object.
(1) Note. The switch of this subclass may be frangible.

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200Electricity: Circuit Makers and Breakers,   appropriate subclasses for switches or particular structure or type, particularly subclass 47 , for limit switches adapted to be actuated by the motion of a machine part, and subclass 61.41, for stationary switch structure having an actuator responsive to the passage of a transient object
  
[List of Patents for class 324 subclass 200]    200MAGNETIC:
 This subclass is indented under the class definition.  Subject matter which includes apparatus to sense and indicate the sensing of a magnetic field and elements or subcombinations of apparatus to sense and indicate the sensing of the magnetic field where not elsewhere provided.
(1) Note. Method claims pertaining to the subject matter of this group of subclasses will be placed with the corresponding apparatus subclasses.
(2) Note. The term "elements" includes magnetic sensors, per se, and energized sensors not provided for in another class.
(3) Note. The apparatus to indicate includes a visible or latent recording of the result of a magnetic field sensing.
(4) Note. The magnetic field sensed may be a portion of a magnetic field or a portion of a magnetic field in a material.
(5) Note. Included in this group of subclasses are: the measuring or testing of magnetic fields, the measuring, testing, or sensing of material of metal or nonmetal by means of magnetic fields for electrical, magnetic, and other properties of the material, subcombinations of the apparatus to measure or test magnetic fields or materials by magnetic fields not provided for elsewhere, magnetic field sensors not classified elsewhere, supports for material tested by magnetic fields, and supports for magnetic field sensing devices.
(6) Note. This is the generic subclass for the location, identification, or testing of (1) metal ores, (2) unwanted metals, or (3) the presence of metal in a nonmetal environment. In these cases the metal is located, identified, or tested by its interaction with a magnetic field.

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51,for short or open coil tests, the number of coil turns tests, and coil polarity tests.
55,for transformer properties testing. 300+, for nuclear or electronic testing. 323+, for geophysical subsurface and surface testing. 376+, for core sample magnetic orientation testing.

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164Metal Founding,   subclass 450.5 for a metal casting apparatus including control means influenced by a magnetic sensor.
209Classifying, Separating, and Assorting Solids,   subclass 8 for magnetizing or demagnetizing precedent to a separation, subclasses 38+ for the combination of a magnetic separation with another physical separation of a solid from a solid, subclasses 72+ for the magnetic testing and separation of objects from other objects, and subclasses 212+ for the separation of material by magnetic separation.
250Radiant Energy,   subclasses 250+ for the detection of invisible electromagnetic energy and the testing of material by invisible electromagnetic radiation, subclasses 493.1+ for radiant energy generation and sources, and subclasses 505.1+ for radiation controlling means.
331Oscillators,   subclass 44 for oscillators with frequency calibration or testing.
343Communications: Radio Wave Antenna,   subclass 17.7 for radar systems with testing or calibrating, and subclass 703 for antennas with means to measure radiated antenna signal energy.
356Optics: Measuring and Testing,   subclasses 33+ for the measurement of distance by light, subclasses 300+ for the examination of visible light by spectros copy, subclasses 138+ for angle or axial alignment testing, subclass 625 for menstruation or conation comparison, subclasses 401+ for color tests, and subclasses 213+ for the examination of visible light generally.
360Dynamic Magnetic Information Storage or Retrieval,   subclass 31 for monitoring or testing the progress of recording.
455Telecommunications,   subclasses 67.11 through 67.7, 115.1-115.4, and subclasses 226.1-226.4 for measuring and testing of communication equipment.
  
[List of Patents for class 324 subclass 201]    201Susceptibility:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field is responsive to a magnetic field modified by material which has magnetic properties, the indication of the sensing being directly or indirectly representative of the ease with which the material can be magnetized.
(1) Note. The ratio of the intensity of magnetization of the material to the magnetic intensity of the field causing the magnetization of the material is known as susceptibility.

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204,for apparatus to test gas, liquids, and fluent particles entrained in a fluid.
228,for apparatus to test materials which require a magnetic test field including torque magnetometers.
  
[List of Patents for class 324 subclass 202]    202Calibration:
 This subclass is indented under subclass 200.  Subject matter which includes means to present a known magnetic field to the apparatus to sense and indicate the sensing of the magnetic field so that the sensing and indication can be noted to see if the apparatus to sense and indicate gives the correct response to the sensed known magnetic field.
(1) Note. The known magnetic field may be a magnetic field of known magnetic intensity and type of wave, or the field can be a known magnetic field which is modified by a member whose effect on the field is known.

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74,for testing and calibrating electric meters.
130,for self-calibrating instruments which measure voltage or current.

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73Measuring and Testing,   subclasses 1.01+ for proving or calibrating test instruments.
250Radiant Energy,   subclass 252.1 for methods of calibration or standardization of radiant energy test devices.
356Optics: Measuring and Testing,   subclass 46 for electrical lamp circuits forming light standards, and subclasses 421+ for color charts.
374Thermal Measuring and Testing,   subclasses 1+ for calibration or testing of a thermally responsive instrument.
  
[List of Patents for class 324 subclass 203]    203Curie point determination:
 This subclass is indented under subclass 200.  Subject matter which includes means to create a magnetic field in which is placed a heated ferromagnetic material, the apparatus to sense and indicate being responsive to the magnetic field modified by the heated material to determine whether the heated material is at least at or below the critical temperature at which the heated material loses its ferromagnetism.
(1) Note. The apparatus to sense and indicate the magnetic field may be a magnet which functions to pass its magnetic flux through the material to induce magnetism in the material if its temperature is below the Curie point of the material to attract the material to the magnet.

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224,for the temperature control of the test material or an element of the test circuit.
228,for permanent magnets which locate ferromagnetic material by inducing magnetism in the material and noting the relative movement of the permanent magnet to material to be located.

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148Metal Treatment,   particularly subclasses 195+ for flame cutting or burning combined with sensing, subclasses 215+ for processes of carburizing or nitriding of metal combined with sensing or testing, subclass 240 for testing combined with reactive coating of metal, or subclasses 508+ for processes of measuring, testing, or sensing combined with treatment of solid or semi-solid metal to modify or maintain the internal physical structure (i.e., microstructure) or chemical property of metal. If casting, fusion bonding, machining, or working is combined with the treatment of solid or semi-solid metal to modify or maintain the internal physical structure (i.e., microstructure), there is a requirement that there be significant heat treatment as defined in section III, A, of the Class 148 definition.
335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 209+ for magnets and electromagnets.
340Communications: Electrical,   subclass 597 for a ferromagnetic temperature sensor in a signalling system; and subclasses 577 and 600 for ferromagnetic flame and radiation sensors, respectively, in a signalling system.
356Optics: Measuring and Testing,   subclasses 43+ for optical pyrometers.
361Electricity: Electrical Systems and Devices,   subclass 158 for temperature indicating instruments with systems for magnetizing, demagnetizing, or controlling a magnetic field.
374Thermal Measuring and Testing,   subclass 176 for a thermometer having a ferromagnetic sensor.
  
[List of Patents for class 324 subclass 204]    204Fluid material examination:
 This subclass is indented under subclass 200.  Subject matter which includes a magnetic field in which a gas or liquid material is placed for examination by the magnetic field, the apparatus to sense and indicate being responsive to the field modified by the gas or liquid material to give an indication of some property of the material examined.
(1) Note. Particles may be entrained in the gas or liquid examined magnetically in this subclass.

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23Chemistry: Physical Processes,   subclasses 232+ for gas analysis processes.
73Measuring and Testing,   subclasses 23+ for gas analysis, particularly subclass 27 for paramagnetic gas analysis by magnetic and thermal means, and subclass 194 for magnetic induction type flow meters.
95Gas Separation: Processes,   subclasses 27 and 28 for processes of gas separation using magnetism.
96Gas Separation: Apparatus,   subclasses 1+ for magnetic separation means for gas separation.
209Classifying, Separating, and Assorting Solids,   subclasses 38 through 40for the magnetic separation of a solid from a solid, liquid, or a gas combined with another type of separation, and subclass 232 for the separation of a solid from a solid or liquid magnetically when in a fluid suspension.
210Liquid Purification or Separation,   subclass 695 for processes of precipitation of a solid from a liquid by magnetic means, and subclasses 222+ for apparatus to magnetically treat material under the class definition.
250Radiant Energy,   subclass 306 for the inspection of liquids by electrically charged particles, subclasses 343+ for the infrared examination of contained fluent material, subclass 356.1 for flow metering by radiant energy apparatus, subclass 357.1 for fluent material level examination by radiant energy, subclasses 373+ for the ultraviolet examination of contained fluent material, subclasses 383+ for the examination of emissive fluent type or radiation transmissive fluent material by ionized gas-type detector, subclasses 428+ for fluent material containment, support, or transfer means combined with radiant energy treatment, subclasses 564+ for photocell sensing of fluent material, and subclasses 573+ for optical or prephotocell systems to sense fluent material by photoelectric means.
356Optics: Measuring and Testing,   subclass 70 for oil testing by visible light; subclass 398 for the inspection of container content by light; subclasses 409+ for color transmission testing of fluids; and subclasses 441+ for the examination of liquid particle suspensions by visible light.
422Chemical Apparatus and Process Disinfecting, Deodorizing, Preserving, or Sterilizing,   subclasses 83+ for analysis of apparatus involving a chemical reaction.
  
[List of Patents for class 324 subclass 205]    205Permanent magnet testing:
 This subclass is indented under subclass 200.  Subject matter which involves the testing of permanent magnets which have their own static magnetic field, the apparatus to sense and indicate the sensing of the field including a field sensing member placed in the field and an indicator responsive to the member.
(1) Note. The sensing member may be a fixed or movable permanent magnet, a member that can be temporarily magnetized by the field of the tested magnet, an electrically conductive member that causes eddy currents in response to the field, or a sensing coil that is fixed or movable.

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228,for the testing of material by a magnetic field and the sensing of the material modified field by a nonelectrically energized field sensor.
256,for the sensing of a magnetic field by a movable energized sensing coil magnetometer.
259,for a magnet or magnet member sensor type magnetometer.

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335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 302+ for permanent magnets.
  
[List of Patents for class 324 subclass 206]    206Movable random length material measurement:
 This subclass is indented under subclass 200.  Subject matter which includes a movable magnetizable member and a magnetic marking means to form magnetic field marks on the member in the direction of its movement, and wherein the apparatus to sense and indicate the sensing of the magnetic field is responsive to the marks and indicates the sum of the marks as an indication of its length or compares the sensed marks to indicate a deviation of its length between markings.

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33Geometrical Instruments,   subclasses 732+ for feeding a fabric or cord through a fabric or cord distance measuring device in contact with the fabric or cord.
226Advancing Material of Indeterminate Length,   subclasses 10+ for control means actuated in response to marks on advancing material.
242Winding, Tensioning, or Guiding,   subclass 431 for a winding machine under the control of an electrical property of an article being wound, and subclasses 334.3, 334.4, 485.5, 487.5, 534+, and 563+ for a detector or stop which may measure length of an elongated material being wound or unwound.
333Wave Transmission Lines and Networks,   subclasses 141+ for electromechanical transducer-type time delays.
360Dynamic Magnetic Information Storage or Retrieval,   subclasses 1+ for recording or reproducing from an element of diverse utility, and subclass 6 for recording or playback apparatus combined with metering or sensing.
  
[List of Patents for class 324 subclass 207.11]    207.11Displacement:
 This subclass is indented under subclass 200.  Subject matter which includes a device to note the change in position of one member with respect to another member, the device having means to create a magnetic field and having either (1) the means supported by one of the members, or (2) the members included in a magnetic circuit in the magnetic field, the apparatus to sense and indicate the sensing of the magnetic field being responsive to the change in the magnetic field to note the movement of one of the members with respect to the other member.

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178Telegraphy,   subclasses 18.01+ for position determining or writing (e.g., hand writing analysis).
341Coded Data Generation or Conversion,   subclass 15 for a displacement responsive magnetic pattern element with a digital code signal generating circuit.
  
[List of Patents for class 324 subclass 207.12]    207.12Compensation for measurement:
 This subclass is indented under subclass 207.11.  Subject matter which includes a device, circuit or circuit component that corrects an undesirable condition which affects the displacement measurement.
  
[List of Patents for class 324 subclass 207.13]    207.13Having particular sensor means:
 This subclass is indented under subclass 207.11.  Subject matter which includes a device having a specific function or structure that detects the presence of, or a change in the level of a magnetic field.
  
[List of Patents for class 324 subclass 207.14]    207.14Diverse sensors:
 This subclass is indented under subclass 207.13.  Subject matter in which two or more different types of sensors are used simultaneously or alternatively.
(1) Note. Plural measurements involve two or more different types of measurements such as linear and rotary, whereas diverse measurement includes two or more sensors for one or more measurements.

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207.23,for plural measurements.
  
[List of Patents for class 324 subclass 207.15]    207.15Inductive:
 This subclass is indented under subclass 207.13.  Subject matter wherein sensing device is an inductor.

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336Inductor Devices,   appropriate subclasses for inductors not specifically used in testing.
  
[List of Patents for class 324 subclass 207.16]    207.16Electrically energized:
 This subclass is indented under subclass 207.15.  Subject matter containing one or more sources of electrical energy for energizing sensor means to produce a magnetic field.
  
[List of Patents for class 324 subclass 207.17]    207.17Separate pick-up:
 This subclass is indented under subclass 207.16.  Subject matter in which a magnetic sensor is a receiver means that generates a signal in response to an electrically energized transmitter.
  
[List of Patents for class 324 subclass 207.18]    207.18Differential type (e.g., LVDT):
 This subclass is indented under subclass 207.16.  Subject matter wherein (1) a sensor measures two separate stimuli and provides an output proportionate to the difference between them or (2) a transformer uses two or more primary sensor signals, or (3) a transformer uses two or more secondary sensor signals to provide a differential output.
(1) Note. LVDT is an abbreviation meaning linear variable differential transformer.
  
[List of Patents for class 324 subclass 207.19]    207.19Differential bridge circuit:
 This subclass is indented under subclass 207.16.  Subject matter wherein an imbalance in a bridge circuit is based upon the difference between at least two inductive sensors forming at least two legs of the bridge circuit.
  
[List of Patents for class 324 subclass 207.2]    207.2Hall effect:
 This subclass is indented under subclass 207.13.  Subject matter wherein the sensor uses the Hall effect to give an output voltage proportional to magnetic field strength.
(1) Note. Hall effect is the description given to the following phenomena: when a conductor, through which a current is flowing, is placed in a magnetic field, a potential difference is generated between the two opposed edges of the conductor in the direction mutually perpendicular to both the field and the conductor.

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251,for hall plate magnetometers.

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330Amplifiers,   subclass 6 for hall effect amplifiers.
338Electrical Resistors,   subclass 32 for resistance value responsive to a condition wherein magnetic field or compass utilizes Hall effect.
  
[List of Patents for class 324 subclass 207.21]    207.21Magnetoresistive:
 This subclass is indented under subclass 207.13.  Subject matter wherein a sensor is a semiconductor material in which the electrical resistance is a function of the applied magnetic field.

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252,for Hall plate magnetoresistive magnetometer.

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338Electrical Resistors,   subclass 32 for a magnetic field or compass with resistance value responsive to a condition.
  
[List of Patents for class 324 subclass 207.22]    207.22Having particular sensed object:
 This subclass is indented under subclass 207.11.  Subject matter in which a specific configuration or structure of an object is such that its motion may be detected by measuring a change of a magnetic property associated with the object.
(1) Note. This subclass includes sensor attachments that move with the device under test.
  
[List of Patents for class 324 subclass 207.23]    207.23Plural measurements (e.g., linear and rotary):
 This subclass is indented under subclass 207.11.  Subject matter wherein there are two or more different types of position measurement.

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207.14,for measurements using two or more sensors.
  
[List of Patents for class 324 subclass 207.24]    207.24Linear:
 This subclass is indented under subclass 207.11.  Subject matter in which motion in a straight line is determined.
  
[List of Patents for class 324 subclass 207.25]    207.25Rotary:
 This subclass is indented under subclass 207.11.  Subject matter in which (1) angular displacement is determined or (2) deviation from an angular path is measured.
  
[List of Patents for class 324 subclass 207.26]    207.26Approach or retreat:
 This subclass is indented under subclass 207.11.  Subject matter in which the (1) the sensing device gives an indication when approaching or being approached by a magnetic field, or (2) the sensing device gives an indication when retreating or being retreated by a magnetic field, or (3) an object approaches or retreats from the sensor"s magnetic field.
  
[List of Patents for class 324 subclass 209]    209Stress in material measurement:
 This subclass is indented under subclass 200.  Subject matter which includes apparatus to note the strain within material having means to form a magnetic field in which the material is placed, or means to form a magnetic field in the material, the apparatus to sense a magnetic field and indicate the sensing of the magnetic field senses the magnetic field modified by the material or the field produced in the material and indicates the result of the test, the indication being a measure of the strain in the material as a result of some type of force imparted to or within the material.
(1) Note. The means to impart the force to the material may or may not be claimed.
(2) Note. Compressional, tensional, shear, or torsional physical force is used to impart strain to the material.
(3) Note. The material tested can be examined for residual strain after the applied force is removed from the material, or the material can be examined for strain resulting from the applied force.
(4) Note. Excluded are claims to sense the internal strain of a magnetic sensor which is an indication of the force applied to the sensor and torque or torsion sensing devices relying on magnetic characteristics.
(5) Note. Claims testing the magnetostrictive effect of material are classifiable here.

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73Measuring and Testing,   subclasses 136+ and 141+ for sensing the internal strain of a magnetic sensor which is an indication of the force applied to the sensor and torque or torsion sensing devices relying on magnetic characteristics; subclass 779 for stress or strain measuring system having an inductive or magnetic sensor mechanically coupled to the specimen and subclasses 862+ for dynamometers including subclasses 862.381+ for the measurement of force by magnetic load cells.
356Optics: Measuring and Testing,   subclasses 32+ for material strain analysis of material by visible light.
  
[List of Patents for class 324 subclass 210]    210Magnetic information storage element testing:
 This subclass is indented under subclass 200.  Subject matter which includes a magnetic recorder element to be tested magnetically, means to create a magnetic test signal to be either sensed by the tested element or recorded on the tested element, the said apparatus to sense the magnetic field either (1) being or including the tested element itself, or (2) sensing the recorded test signal on the tested element, the said apparatus to indicate the sensing of the test magnetic signal being responsive to the apparatus to sense the signal or to the recorder element tested.
(1) Note. The testing device is not integral with the information device tested.
(2) Note. A prerecorded test signal on a magnetic storage element tested may take the place of the means to create a test signal.

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29Metal Working,   subclass 603 for processes of making magnetic recording reproducing transducers.
346Recorders,   subclass 33 for a magnetic recorder with an external operating means, and subclass 74.2 for magnetic pictorial or graphic recorders.
365Static Information Storage and Retrieval,   subclass 201 for specifics of a memory which are tested for defects or erroneous information.
702Data Processing: Measuring, Calibrating, or Testing,   subclasses 108+ for testing system, particularly subclasses 117+ for testing of circuit.
714Error Detection/Correction and Fault Detection/Recovery,   subclasses 718+ for diagnostic testing of memory systems.
  
[List of Patents for class 324 subclass 211]    211Memory core storage element testing:
 This subclass is indented under subclass 210.  Subject matter wherein the element tested is a nonmoving toroid magnetic memory element.

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209Classifying, Separating, and Assorting Solids,   subclass 81 for the automatic magnetic testing and sorting of static cores.
365Static Information Storage and Retrieval,   subclasses 129+ for toroid magnetic elements in a memory system.
  
[List of Patents for class 324 subclass 212]    212Dynamic information element testing:
 This subclass is indented under subclass 210.  Subject matter wherein the element tested is a movable magnetic storage element.
(1) Note. Here are magnetic tape, drum, disc, and wire storage elements.

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360Dynamic Magnetic Information Storage or Retrieval,   subclass 31 for testing the progress of recording.
  
[List of Patents for class 324 subclass 213]    213Magnetic recording medium on magnetized object records object field:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field includes a magnetic recording medium applied to magnetized material so that any stray or leakage field from the magnetized material induces a magnetic field in the recording medium which is indicative of flaws in the material tested.
(1) Note. The magnetic field of the recording medium is latent and requires, for example, magnetic particles to form a visible image of the induced field on the recording medium.

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210+,for the testing of magnetic information storage elements.
214+,for testing of magnetic fields or magnetized materials by magnetic particles.

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209Classifying, Separating, and Assorting Solids,   subclass 215 and other related subclasses for separation of flawed articles from good magnetized articles based upon the change in the magnetic field of magnetized article due to flaws in the article.
252Compositions,   subclass 62.52 for flaw detections compositions.
346Recorders,   subclass 33 for the recording of flaws in response to an external flaw detection device.
  
[List of Patents for class 324 subclass 214]    214By paramagnetic particles:
 This subclass is indented under subclass 200.  Subject matter which includes a magnetic field detector composed of particles including ferromagnetic material which, when placed in the magnetic field, align themselves in the direction of the tested magnetic field to form a visual representation of the tested magnetic field.
(1) Note. The particles may be of iron, nickel, or cobalt material.
(2) Note. The particles when in the magnetic field act as both a magnetic field detector and a visual indicator of the pattern of the tested field at the location of the field between the magnetic poles or at the location of the field discontinuities.

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200,for the sensing and plotting of magnetic fields.

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252Compositions,   subclass 62.51 for magnetic compositions useful for magnetic purposes.
  
[List of Patents for class 324 subclass 215]    215With pattern enhancing additive:
 This subclass is indented under subclass 214.  Subject matter wherein some chemical, composition, material, or mixture of materials is added to the paramagnetic particles to enhance the viewing of the particles with respect to the object tested after the particles are magnetized and attracted to the magnetized object tested.
(1) Note. The chemical, composition, material, or mixture may be directly placed on or diffused some way into the magnetic particles, or may form a dry mixture with the particles or a liquid vehicle for the magnetic particles.
(2) Note. Coatings, dyes, and liquid and solid mixtures of material with the particles are in this subclass.
(3) Note. Fluorescent and phosphorescent material which require radiation on these materials to emit light are here as well as materials which have optical properties to permit the particles to be more easily distinguished from the object and the surroundings of the test.
  
[List of Patents for class 324 subclass 216]    216Flaw testing:
 This subclass is indented under subclass 214.  Subject matter wherein the paramagnetic particles are used to test an object made of magnetic material and which includes means to magnetize the object to be tested to cause the parmagnetic particles, when upon the magnetized object, to become magnetized and adhere to the magnetized object or at a location where a discontinuity occurs when present in the object, the adhering magnetized particles arranging themselves in the pattern of the flux exiting from the object or in the pattern of a discontinuity when present in the object.
(1) Note. The magnetization may be caused by direct electrical current, by alternating current, by alternating and direct current, or by a permanent magnet.
(2) Note. A discontinuity is a flaw which includes a crack, fault, or other defect that is present in a tested object that is capable of changing the magnetization pattern known to be formed from a perfect object.

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213,for the detection of flaws by magnetizing a material with a magnetic recording medium thereon to record the field of the magnetized material.
215,for particles with additives to enhance the viewing of magnetized particles.
217+,for flaw detection of railroad rails.
452+,for the use of particles to test flaws by electrostatic forces.

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73Measuring and Testing,   subclasses 632+ for flaw detection by means of compressional waves.
250Radiant Energy,   subclass 358.1 for pipe inspection by invisible radiant energy, and for tire inspection by invisible radiation, subclasses 559.45+ for the photoelectric sensing of web, strand, or sheet material for defects by visible light.
356Optics: Measuring and Testing,   particularly subclasses 430+ for flaw detection in webs; and subclasses 237.1+ for flaw testing generally.
374Thermal Measuring and Testing,   subclasses 4+ for flaw detection by a thermal determination.
378X-Ray or Gamma Ray Systems or Devices,   subclasses 58+ for X-ray flaw analysis.
  
[List of Patents for class 324 subclass 217]    217Railroad rail flaw testing:
 This subclass is indented under subclass 200.  Subject matter which includes means to magnetize a railroad rail to create a test magnetic field in the rail, the apparatus to sense and indicate the sensing of the magnetic field being responsive to the field of the rail to note any change in the indication from the normal known magnetic pattern of the magnetized rail.
(1) Note. The subcombinations of means to magnetize a rail and of means to sense the magnetization of the rail are classified here.

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62+,for the resistance testing of rails.
65,particularly for the flaw testing of rails by resistance means.

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73Measuring and Testing,   subclasses 636+ for the testing of rails for flaws by vibration.
346Recorders,   subclass 33 for a marking device which is responsive to a magnetic rail flaw detection device.
  
[List of Patents for class 324 subclass 218]    218Rail joint cutout:
 This subclass is indented under subclass 217.  Subject matter wherein the tested rail has ends and is joined to other rails by connectors forming joints between the rails, and includes means to prevent the sensing and indicating of the magnetic field of the joints by the apparatus to sense and indicate the sensing of the magnetic field of the rail.
  
[List of Patents for class 324 subclass 219]    219Magnetic sensor within material:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense a magnetic field includes a sensor placed within tested material which has magnetic field associated with it, the apparatus to indicate the sensing of a magnetic field being responsive to the magnetic field of the material sensed by the sensor.
  
[List of Patents for class 324 subclass 220]    220Sensor supported, positioned, or moved within pipe:
 This subclass is indented under subclass 219.  Subject matter wherein the material tested is a tube and the sensor has (1) means to transport the sensor through the tube, or (2) a support to position or hold the sensor within the tube.
(1) Note. The subcombination of a magnetic sensor and a support to hold, position, or move the sensor within a pipe is here.
(2) Note. An indicator of the distance traveled by the magnetic sensor in the pipe may be additionally claimed.

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260,for magnetic sensors with a support generally.
262,for magnetic sensor supports, per se.

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33Geometrical Instruments,   subclass 700 for bore extensometers, subclasses 772+ for rolling contact-type tube interior gauges, subclasses 792+ for internal dial gauges, and subclasses 814+ for screw adjustment type inside or inside-outside gauges.
250Radiant Energy,   subclass 358.1 for pipe inspection by radiant energy examination.
378X-Ray or Gamma Ray System or Devices,   subclasses 59+ for X-ray pipe testing.
  
[List of Patents for class 324 subclass 221]    221Borehole pipe testing:
 This subclass is indented under subclass 220.  Subject matter wherein the tested pipe is a casing or a borehole in the earth.

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345,for geological and subsurface testing for materials by a magnetic test.

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33Geometrical Instruments,   subclasses 302+ for borehole interior study processes, and subclasses 304+ for borehole direction or inclination meters.
73Measuring and Testing,   subclasses 152.01+ for borehole and drilling study apparatus.
166Wells,   subclass 64 for time or distance measuring, subclass 65.1 for electrical means combined with a well, and subclasses 250.01+ for processes involving indicating, testing, measuring, or locating within a well.
175Boring or Penetrating the Earth,   subclass 4.51 for boring or penetrating with orienting or indicting.
250Radiant Energy,   subclasses 253+ for geological testing or irradiating with radiant energy.
361Electricity: Electrical Systems and Devices,   subclasses 248+ for igniting systems for explosive devices within a well bore.
367Communications, Electrical: Acoustic Wave System and Devices,   subclasses 14+ for compressional wave geophysical systems, and subclass 86 for well bore electrical communications.
436Chemistry: Analytical and Immunological Testing,   subclasses 25+ for geochemical exploration.
  
[List of Patents for class 324 subclass 222]    222Hysteresis or eddy current loss testing:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field includes apparatus to measure the loss of energy of a cyclically varying magnetic field resulting from it passage through a magnetic material or through a material in which eddy currents are induced by the varying magnetic field.

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57,for mutual inductance tests to determine inductance which cause eddy currents.
113,for recording the result of an electrical measurement.
121,for a cathode-ray tube indication of an electrical measurement.
142,for the measurement of electrical real power.
451,for power loss testing of magnetic material by causing heat by passing cyclic current through the material and measuring the power which causes the heat.
  
[List of Patents for class 324 subclass 223]    223Hysteresis loop curve display or recording:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field is responsive to a material magnetized by a changing magnetic field going from a minimum to a maximum in one direction and than going from a minimum to a maximum in the opposite direction and produces a signal applied to a visual display or recorder which is the magnetization curve of the material.

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313Electrical Lamp and Discharge Devices,   subclasses 1+ for cathode-ray tube circuits of general application, and subclasses 364+ for deflection circuits for a cathode-ray tube.
346Recorders,   subclasses 33+ for recorders combined with external recorder operating means.
347Incremental Printing of Symbolic Information,   subclasses 226+ for recorders operated by a light beam including a cathode ray beam.
  
[List of Patents for class 324 subclass 224]    224With temperature control of material or element of test circuit:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field is also responsive to magnetic fields modified by tested materials placed in a magnetic field and includes means to control the temperature of the material tested or some element of the apparatus to sense and indicate the sensing of the magnetic field.
(1) Note. The means to control the temperature includes heating and cooling.

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248,for superconductive magnetometers which require low temperatures to function.

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62Refrigeration,   appropriate subclasses for devices to cool.
73Measuring and Testing,   subclasses 15+ for thermal tests, and subclasses 339+ for temperature measuring means, per se.
148Metal Treatment,   subclass 121 for the heat treatment of magnetic materials to intentionally change the magnetic properties, and subclass 509 for heat treatment of solid or semi-solid metal to modify or maintain the internal physical structure (i.e., microstructure) or chemical property of metal combined with the measuring, sensing, or testing of magnetic properties.
165Heat Exchange,   particularly subclass 58 for heating and cooling.
219Electric Heating,   subclasses 50+ for metal heating, and subclass 200 for heating devices for nonmetals.
361Electricity: Electrical Systems and Devices,   subclass 140 for thermal change compensation for electromagnetic device control circuits, and subclass 141 for superconductivity electromagnetic device control circuits.
432Heating,   appropriate subclass for the heating of materials nonelectrically.
  
[List of Patents for class 324 subclass 225]    225With compensation for test variable:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of the magnetic field includes structure to correct for some condition which affects the test.
(1) Note. The magnetic field tested may be a magnetic field, per se, or a magnetic field modified by a material under test.
(2) Note. The condition may be magnetic interference, the spacing of the material tested with respect to the magnetic sensing means, or some condition of the apparatus to sense and indicate.

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224,for temperature control of the tested material or an element of the test circuit.
244,for magnetometers having disturbing magnetic field compensation.
  
[List of Patents for class 324 subclass 226]    226Combined:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field is combined with the subject matter of another class when not provided for elsewhere.
(1) Note. The examination of material by magnetic fields and the testing of magnetic fields are here when combined with other subject matter.
(2) Note. In combination with magnetic testing are: demagnetizing, the conveying of material to or from the test, or the conveying of the magnetic test apparatus, diverse test apparatus of other classes and subject matter of other classes.

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157,for measuring or sensing electricity combined with other subject matter.

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194Check-Actuated Control Mechanisms,   subclasses 320+ for material testers which use magnets.
209Classifying, Separating, and Assorting Solids,   subclasses 38+ for the separation of solids from solids by magnetizing means and other separation means, subclasses 567+, 609, and 636 for article separating means involving magnetism, and subclasses 212+ for the separation of magnetic material from other material which is nonmagnetic or less magnetic.
356Optics: Measuring and Testing,   subclass 72 for the combination of an optical test with other subject matter.
  
[List of Patents for class 324 subclass 227]    227Plural tests:
 This subclass is indented under subclass 200.  Subject matter wherein (1) two or more variable magnetic parameters are separately sensed and indicated, at least one of which is sensed and indicated by apparatus to sense and indicate the sensing of a magnetic field, or (2) at least one of two or more separate tests is a magnetic test.
(1) Note. The separate tests may be performed sequentially or simultaneously.
(2) Note. A. Subject matter of this subclass includes, for example, permeameters wherein a sensed voltage is used to indicate a change in flux for a given value of magnetomotive force indicated by the current causing the force. B. Subject matter of this subclass includes, for example, (1) a nonmagnetic hardness test combined with a magnetic flaw test, or (2) two simultaneous but spatially separated magnetic flaw tests.

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403+,for lamp and discharge device tests involving plural diverse characteristics or conditions.
  
[List of Patents for class 324 subclass 228]    228With means to create magnetic field to test material:
 This subclass is indented under subclass 200.  Subject matter which includes structure to form a magnetic field for testing material, the apparatus to sense and indicate the sensing of the magnetic field being responsive to the field as modified by the material tested.
  
[List of Patents for class 324 subclass 229]    229Thickness measuring:
 This subclass is indented under subclass 228.  Subject matter wherein the material tested has two different surfaces, and the distance between the surfaces is measured by placing the two surfaces in the magnetic field and the apparatus to sense and indicate the sensing of the field is responsive to the field as modified by the material between the two surfaces to thus sense and indicate the distance between the surfaces.
(1) Note. Class 324 measures thickness by sensing a change in magnetic property of magnetic test. For measuring thickness by having contacts touching the tested material, see the Search Note below.

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33Geometrical Instruments,   measures thickness by having contacts touching the tested material; see subclasses 783+ for distance measuring devices, particularly subclass 835 for coating thickness measurement, and subclasses 174+ for gauges.
73Measuring and Testing,   subclass 37.5 for the measurement of a dimension of a material by fluid means.
250Radiant Energy,   appropriate subclasses for the measurement of a dimension of a material by invisible radiation.
356Optics: Measuring and Testing,   subclass 629 for determining the thickness of light permeable material.
374Thermal Measuring and Testing,   subclass 7 for a thickness determination by a thermal test.
378X-Ray or Gamma Ray Systems or Devices,   subclasses 50 , 54+, and 89+ for X-ray thickness measuring.
  
[List of Patents for class 324 subclass 230]    230Layer of layered material:
 This subclass is indented under subclass 229.  Subject matter wherein the material tested is composed of dissimilar layered material and the thickness of one layer is found by placing the layered material in the magnetic field and the apparatus to sense and indicate the sensing of the magnetic field is responsive to the magnetic field modified by the layer to thus sense and indicate the depth of the layer.
  
[List of Patents for class 324 subclass 231]    231With backing member:
 This subclass is indented under subclass 229.  Subject matter which includes a part next to one surface of the material and the apparatus to sense and indicate the sensing of the magnetic field next to the other surface opposite to the part; the part and the apparatus cooperating with each other to place tested material in the same relation each time with respect to the magnetic field and the apparatus to sense and indicate the sensing of the field.
(1) Note. The part generally but not always is part of the magnetic test circuit.
  
[List of Patents for class 324 subclass 232]    232Plural magnetic fields in material:
 This subclass is indented under subclass 228.  Subject matter which includes means to create two or more magnetic fields in the tested material, the apparatus to sense and indicate the sensing of the magnetic field being responsive to the fields modified by the material to indicate some characteristic of the material.
(1) Note. Included are diverse magnetic fields at the same location in the material, or magnetic fields at different locations in the material, but not two fields of the same type aiding each other at the same place in the material.
  
[List of Patents for class 324 subclass 233]    233With phase sensitive element:
 This subclass is indented under subclass 228.  Subject matter wherein the apparatus to sense and indicate the sensing of the magnetic field modified by the material tested includes an element which compares the electrical phase of the signal as received by the apparatus with the phase of the magnetic field used in the test, the difference in phase being used by the apparatus to show some characteristic of the tested material.
(1) Note. Here are mostly eddy current tests which do not fall out in the preceding subclasses. Eddy current tests not classified here will be found in the subclasses following when no phase detection is claimed.
  
[List of Patents for class 324 subclass 234]    234Electrically energized nonforce type sensor:
 This subclass is indented under subclass 228.  Subject matter wherein the apparatus to sense and indicate the sensing of the magnetic field modified by the material includes a sensor which requires an electrical current to pass therethrough, and which senses and indicates the magnetic field other than by a force measurement.
(1) Note. Included are self-inductance-type field sensors.

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228,for the testing of material magnetically by torque magnetometers and electrically energized sensors of force.
244,for magnetometers.
260,for magnetic sensors not electrically energized.
300+,for the testing of material by nuclear or electronic induction.
323+,for the magnetic testing of material by a magnetic field.
332+,especially, which requires a magnetic field to test material within or part of the upper natural surface of the earth.
  
[List of Patents for class 324 subclass 235]    235Noncoil type:
 This subclass is indented under subclass 234.  Subject matter wherein the energized sensor does not rely solely on inductive effects.
(1) Note. Here are sensors of the magnetoresistive and galvanomagnetic type which includes Hall effect sensors.

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251,for Hall plate magnetometers.
252,for magnetoresistive and semiconductor solid-state magnetometers.

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338Electrical Resistors,   subclass 32 for magnetoresistive and for Hall effect devices, per se.
  
[List of Patents for class 324 subclass 236]    236Oscillator type:
 This subclass is indented under subclass 234.  Subject matter wherein the sensor is part of a frequency generator whereby the material-modified magnetic field is sensed by the sensor to control the frequency or the amplitude of the electrical wave generated by the frequency generator.

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234,for sensing material-modified magnetic fields by self-inductive type sensors.

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331Oscillators,   subclass 65 for oscillators with a device responsive to an external physical condition. See subclass 64 of Class 331 for the line between Classes 331 and 324.
  
[List of Patents for class 324 subclass 237]    237Material flaw testing:
 This subclass is indented under subclass 236.  Subject matter wherein the material is magnetically tested for defects in the material.
  
[List of Patents for class 324 subclass 238]    238Material flaw testing:
 This subclass is indented under subclass 234.  Subject matter wherein the material is magnetically tested for defects in the material.
(1) Note. A defect is any blemish, crack, or other inherent imperfection in a material that weakens the material.

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213,for magnetic recording mediums attached to a tested magnetized material to record the material field.
216,for flaw testing of magnetized material with magnetic particles.
217+,for railroad flaw testing.
219+,for flaw testing when the sensor is within the material.
237,for flaw testers of the oscillator type.
  
[List of Patents for class 324 subclass 239]    239Induced voltage-type sensor:
 This subclass is indented under subclass 228.  Subject matter wherein a voltage is induced in an electrical coil as a result of the change in the magnetic test field caused by the material tested.

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219+,for testing material by placing a magnetic sensor within the material tested.
233,for the testing of material by a test device which compares the phase of a test magnetic field with the phase of the signal sensed by the magnetic sensor.
254,for fixed coil magnetometers responsive to a changing magnetic field.
257,for moving coil magnetometers.
260+,for magnetic field detection device sensors of the induced voltage type.

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323Electricity: Power Supply or Regulation Systems,   subclass 355 for transformers to deliver power to a single load.
336Inductor Devices,   particularly subclass 221 for coil and core, and subclasses 222+ and 225+ for electrical windings, per se, which introduce electrical inductance into an electrical circuit.
  
[List of Patents for class 324 subclass 240]    240Material flaw testing:
 This subclass is indented under subclass 239.  Subject matter wherein the material is magnetically tested for defects in the material.

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217+,for rail flaw testing.
219+,for magnetic flaw sensors placed within material tested magnetically.
260+,for magnetic field dated on devices generally including those of the induced voltage type.
  
[List of Patents for class 324 subclass 241]    241Opposed induced voltage sensors:
 This subclass is indented under subclass 240.  Subject matter wherein there are two or more magnetic coil sensors of the magnetic field modified by the test material, the apparatus to indicate the sensing of the field modified by the test material being connected to two or more of the sensors to indicate the difference in the voltages induced in the sensors.
  
[List of Patents for class 324 subclass 242]    242Plural sensors:
 This subclass is indented under subclass 240.  Subject matter wherein there are two or more magnetic coil sensors of the magnetic field modified by the test material, the apparatus to indicate the sensing of the field modified by the test material being connected to two or more of the sensors to indicate the combined sensing of the material-modified field.
  
[List of Patents for class 324 subclass 243]    243Plural sensors:
 This subclass is indented under subclass 239.  Subject matter wherein there are two or more coil sensors of the induced voltage type, the apparatus to indicate the sensing of the magnetic field being connected to two or more of the sensors to note the combined sensing of material-modified magnetic field.
  
[List of Patents for class 324 subclass 244]    244Magnetometers:
 This subclass is indented under subclass 200.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field is responsive to the intensity of the sensed magnetic field or the direction of the sensed magnetic field.
(1) Note. Subject matter classifiable in this subclass includes subcombinations or perfecting features peculiar to magnetometers and not classifiable elsewhere such as field compensating means for magnetometers.

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227,plural magnetic tests of a magnetic field.
228+,for the testing of material by magnetic fields which use magnetometers for the defection of the material-modified magnetic field.

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33Geometrical Instruments,   subclasses 300+ for compasses, particularly subclasses 356+ for magnetic field responsive error compensation.
174Electricity: Conductors and Insulators,   subclasses 32 through 397for anti-inductive structures, particularly subclass 352 for shielded coils.
307Electrical Transmission or Interconnection Systems,   subclass 89 for systems to prevent induction having means to control a magnetic field, and subclass 101 for residual or remnant magnetism control.
361Electricity: Electrical Systems and Devices,   subclass 93.6 for abnormal current condition protection including transformer sensor.
  
[List of Patents for class 324 subclass 244.1]    244.1Optical:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus or method for sensing and indicating a magnetic field includes a medium which responds to the magnetic field by altering the propagation (e.g., path, passage, etc.) or a property (e.g., polarization) of radiant light energy therethrough, where the output of the medium is representative of the magnetic field measured.
(1) Note. This subclass includes physical changes of the light path affecting the light.

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96+,for devices which measure electricity using radiant energy.

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250Radiant Energy,   subclasses 200+ for photocells, circuits, and apparatus.
356Optics: Measuring and Testing,   subclass 450 for optical testing by light wave interference.
359Optics: Systems (Including Communication) and Elements,   subclasses 280+ for changing a bulk optical parameter by an applied magnetic field.
385Optical Waveguides,   subclasses 12+ for environmentally sensing optical waveguides.
  
[List of Patents for class 324 subclass 245]    245Plural sensor axis misalignment correction:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense and indicate the sensing of the magnetic field includes plural magnetic field sensors aligned with each other, the sensors when not aligned with each other producing errors in the magnetic field measurement, and means responsive to the sensing of the magnetic field by both sensors to adjust for the misalignment of the sensors, the apparatus to indicate being connected to the sensors.
  
[List of Patents for class 324 subclass 246]    246With means to align field sensor with magnetic field sensed:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense and indicate the sensing of the magnetic field includes a movable magnetic field sensor of the tested magnetic field and apparatus responsive to the magnetic field connected to the magnetic sensor responsive to the magnetic field to physically move the sensor to a predetermined position with respect to the sensed magnetic field.

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318Electricity: Motive Power Systems,   subclass 647 for electric servo motors under the control of magnetic field sensing sensors.
  
[List of Patents for class 324 subclass 247]    247Nonparallel plural magnetic sensors:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense the magnetic field includes several magnetic sensors positioned angularly with respect to each other so that an axis of another sensor will intersect the other axis and the apparatus to indicate is connected to the several sensors to note the combined sensing of the tested magnetic field.

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227,for plural magnetic tests each having a magnetic field sensor.
228,for magnetic tests to subject material to a magnetic field.
242,particularly for material flaw testing apparatus using plural magnetic coil sensors.
243,for material tests using plural magnetic coil sensors to examine material.

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33Geometrical Instruments,   subclass 300 for indicator of direction of force traversing material media apparatus including direction or inclination instruments, gyromagnetic compasses and magnetic field responsive instruments.
340Communications: Electrical,   subclass 870.33 for continuously variable indicating apparatus having indication transmitters of the magnetic flux sensor type combined with circuitry connected to the transmitters, and subclass 345 for code transmitters which include magnetic flux sensing devices, per se.
  
[List of Patents for class 324 subclass 248]    248Superconductive magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field includes a sensor of the magnetic field or a magnetic shield for the apparatus to sense a magnetic field made of a material which has nearly zero resistance in one state and appreciable resistance in a second state.
(1) Note. Superconductivity is a property possessed by some metals, alloys, or compounds whereby the electrical resistance of the metals, alloys, or compounds decreases until a critical temperature is reached and the resistance becomes practically zero when the temperature of the metal, alloy, or compound is reduced to within a few degrees of absolute zero.
(2) Note. The apparatus to produce the low temperatures in the superconductors in order to permit the superconductors to function as a shield or a magnetic field sensor is not always claimed.

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29Metal Working,   subclass 599 for processes of manufacturing superconductor electrical devices.
323Electricity: Power Supply or Regulation Systems,   subclass 44 for transformer systems using superconductors.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 527+ for miscellaneous superconductive circuits.
331Oscillators,   subclass 107 for superconductive oscillators using a superconductive active element.
335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclass 216 for superconductive magnets and electromagnets.
338Electrical Resistors,   subclass 32 for superconductive resistors, per se.
365Static Information Storage and Retrieval,   subclasses 160+ for superconductive magnetic storage systems.
377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   subclass 93 for electrically operated registers using superconductors.
  
[List of Patents for class 324 subclass 249]    249Thin film magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field includes a thin single domain ferromagnetic film magnetized in a predetermined direction known as the easy axis of the film, the magnetization of the film upon placement in an external magnetic field to be tested assumes a different direction which is the resultant field vector of the film"s easy axis and the tested field axis, means to cyclically change the resultant magnetic field axis of the film, sensing means to note the cyclical changes in the magnetic field of the film caused by the shift of the resultant magnetic field due to the means to cyclically change the resultant magnetic field axis, and the apparatus to indicate being connected to the sensing means to note the result of the cyclical changes in the film.
(1) Note. A thin film is defined as a ferromagnetic element formed so as to have its magnetic domains aligned in a predetermined direction. This is usually done by vapor depositing the film in a magnetic field. In the absence of an external field the magnetization vector or magnetic moment will be aligned with the preferred "easy axis" of magnetization of the film. The "hard axis" of the magnetization of the film is in an orthogonal direction to the "easy axis". A thin magnetic film so formed has uniaxial anisotropy.

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227,for plural separate magnetic tests.
228+,for means to create a magnetic test field and a magnetic sensor to sense the test field.

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257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses, including subclasses 108 , 414, and 421-427, for devices responsive to magnetic field.
307Electrical Transmission or Interconnection Systems,   subclass 403 for nonlinear reactor systems having thin film parametron.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 567 for miscellaneous thin film circuits.
365Static Information Storage and Retrieval,   subclasses 171+ for thin film magnetic signal storage systems.
427Coating Processes,   subclasses 547+ for pretreatment of a substrate or post-treatment of a coated substrate using magnetic field or force, 598+ to directly apply a coating using magnetic field or force.
  
[List of Patents for class 324 subclass 250]    250Electronic tube or microwave magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field includes (1) an ionizable gas tube magnetic field sensor having electrodes connected to appropriate voltages wherein the tested magnetic field causes the gas to ionize at different electrode voltages dependent upon the strength of the magnetic field, (2) an energized vacuum tube magnetic field sensor having a cathode ray beam and one or more electrodes or a fluorescent screen connected to appropriate voltages to attract the beam wherein the tested magnetic field acts to deflect the beam an amount dependent upon the strength of the tested field, or (3) an electrically conductive enclosure magnetic field sensor to which a signal is applied having a ferromagnetic material in the enclosure wherein the tested field affects the material to change the signal passed through the enclosure dependent upon the strength of the field.
(1) Note. The enclosure is a waveguide, resonant cavity, or a transmission line.

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58+,for measuring microwave parameters or using microwave devices for determining nonelectric properties.

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33Geometrical Instruments,   subclass 360 for magnetic field direction indicating apparatus using cathode-ray tubes or photo-electric cells.
250Radiant Energy,   subclass 298 for ionic separation or analysis apparatus using magnetic means to separate or deflections, and subclass 396 for apparatus to deflect or focus a charged particle beam.
313Electric Lamp and Discharge Devices,   subclass 153 for electric lamp and discharge devices having a magnetic device, and subclass 364 for cathode-ray tubes, particularly subclass 421 for the beam deflection means of the cathode-ray tube.
315Electric Lamp and Discharge Devices: Systems,   subclass 399 for cathode-ray tube beam deflection circuits.
333Wave Transmission Lines and Networks,   subclasses 141+ for transmission line systems utilizing magnetic effects.
  
[List of Patents for class 324 subclass 251]    251Hall plate magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field includes a thin sheet of conductive material whose thickness is small compared to a dimension of the sides of the sheet, electrical means connected at first diametrical points on the edge of the sheet to pass an electrical current through the sheet, electrical output means connected to second diametrical points on the edge of the sheet at right angles to the first diametrical points and the apparatus to indicate being connected to the electrical output means whereby the solid-state sheet when placed in a magnetic field to be measured normal to the first diametrical points will cause a voltage, consistent with the intensity of the tested magnetic field, at the second diametrical points, which voltage is sensed by the apparatus to indicate.
(1) Note. Compensation for misalignment of axis by means of potential balancing is here.
(2) Note. Hall plates may be made of germanium, bismuth, tellurium, copper, or indium antimonide.

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117,for measuring electricity, per se, with a Hall effect device.
127,for measuring current in a split core transformer with a Hall effect device.
207.2,for magnetic displacement measurement wherein a sensor utilizes the Hall effect.

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310Electrical Generator or Motor Structure,   subclass 3 for Hall effect generators or converters.
323Electricity: Power Supply or Regulation Systems,   subclass 368 for impedance systems including a Hall effect resistor.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 511 for miscellaneous circuits having Hall effect devices sensitive to external magnetic effects.
329Demodulators,   appropriate subclasses for magnetic demodulators which include Hall effect devices.
330Amplifiers,   subclass 6 for amplifiers using the Hall effect.
332Modulators,   subclass 172 for magnetic amplitude modulators using the Hall effect.
338Electrical Resistors,   subclass 32 for Hall effect devices, per se.
365Static Information Storage and Retrieval,   subclass 170 for Hall effect magnetic signal storage devices.
  
[List of Patents for class 324 subclass 252]    252Semiconductor type solid-state or magneto-resistive magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense and indicate the sensing of a magnetic field includes (1) a resistance of magnetic material having a current flow there-through and an indicator connected to the resistance whereby the magnetic field tested passing through the material changes the current noted on the indicator, or (2) a sensor of semiconductor material having a current flow therethrough and an indicator connected to the sensor to note the change in current caused by the tested magnetic field acting on the sensor.
(1) Note. Subject matter of this subclass type includes, for example, p-n junction semi-conductor sensors wherein the current flow therethrough is used to indicate the magnetic field.

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207.21,for magnetic displacement measurement wherein a sensor is magnetoresistive.
228,for noncoil type magnetic sensors including transistors and other solid-state magnetic sensors responsive to a magnetic field modified by a tested material.

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257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses, including subclasses 108 , 414, and 421-427, for devices responsive to magnetic field.
323Electricity: Power Supply or Regulation Systems,   for circuits including active solid-state devices controlled by a magnetic field which controls the voltage or current in the circuits.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 510+ for miscellaneous circuits and systems subjected to external magnetic effects.
330Amplifiers,   subclass 62 for magneto-resistive-type amplifiers.
338Electrical Resistors,   subclass 32 for magnetic field-type resistors.
360Dynamic Magnetic Information Storage or Retrieval,   subclass 113 for information type magnetoresistive transducer structures.
361Electricity: Electrical Systems and Devices,   subclass 235 for control circuits for electromagnetic devices having barrier layer devices controlled by a magnetic field.
365Static Information Storage and Retrieval,   subclass 158 for magnetoresistive storage systems.
  
[List of Patents for class 324 subclass 253]    253Saturable core magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field includes a ferromagnetic core having an alternating magnetic flux passing through the core, the magnetic field tested being concurrently passed through the core with the alternating flux and an electrical coil to sense the change in the magnetic flux caused by the magnetic field in the core, the apparatus to indicate being responsive to the electrical coil sensing the magnetic field change in the core.

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228,for the magnetic testing of material.
236+,particularly, which use coil-type magnetic field sensors.

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33Geometrical Instruments,   subclass 361 for flux gate sensors used in magnetic field responsive instruments indicating the direction of force traversing natural media.
318Electricity: Motive Power Systems,   subclass 47 for magnetic field sensors that control an electric motor servo-system.
340Communications: Electrical,   subclass 870.33 for continuously variable indicating apparatus having an inductor of the flux gate type.
341Coded Data Generation or Conversion,   subclasses 20+ and 173+ for a code transmitter having a flux gate magnetic sensor.
360Dynamic Magnetic Information Storage or Retrieval,   subclass 111 for flux gate magnetic sensing heads to sense or record information.
361Electricity: Electrical Systems and Devices,   subclass 93.6 for abnormal current condition protection including transformer sensor, and subclasses 143+ for drive circuits for flux gate magnetic sensing devices which create the alternating flux for the sensing devices.
  
[List of Patents for class 324 subclass 254]    254Second harmonic type:
 This subclass is indented under subclass 253.  Subject matter wherein the electrical coil sensing the change in the magnetic field in the core is connected to the apparatus to indicate by means of a circuit which passes only a harmonic signal of the alternating magnetic flux impressed upon the core so that the apparatus to indicate the result of the sensing is responsive only to the harmonic signal passed by the circuit.
  
[List of Patents for class 324 subclass 255]    255Peak voltage type:
 This subclass is indented under subclass 253.  Subject matter wherein the composite alternating flux and the magnetic field tested produce a cyclically alternating magnetic flux in the core which will produce peak flux values each half cyclic of the alternating flux although the peaks are not symmetrical half waves of flux, and wherein electrical circuitry connected between the electrical sensing coil and the apparatus to indicate the sensing of the field determines the (1) peak value, (2) the difference in the peak value, or (3) the average value of the voltage induced in the sensing coil caused by the alternate half cycles of the flux in the core.
  
[List of Patents for class 324 subclass 256]    256Energized movable sensing coil magnetometers:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field is a movable electrically energized magnetic field sensing coil, the magnetic field created by the coil interacts with the magnetic field tested to produce a force which moves the sensing coil, and the apparatus to indicate the sensing of the field is connected to the coil to note the movement of the coil.
(1) Note. The magnetic field created in the sensing coil may be a steady state or a changing magnetic field.
(2) Note. The sensing coil may turn or be vibrated by the force caused by the interaction of the tested magnetic field with the field of the sensor.

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236,for magnetic field sensors of the coil type which sense the change in a magnetic field caused by a tested material.
260,for magnetic field sensors of the induction type not classified elsewhere.
  
[List of Patents for class 324 subclass 257]    257Moving coil magnetometer:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field is a movable magnetic field sensing coil placed within the field to be tested and has means to move the movable coil, and the apparatus to indicate the sensing of the magnetic field is connected to the sensing coil whereby the coil moving in the tested field has induced therein a voltage proportional to the number of turns of the coil and the time it takes for the moving coil to complete a cycle of movement.
(1) Note. The sensing coil may or may not have a ferromagnetic core.
(2) Note. The movement may be rotary, vibrator, or translatory.
(3) Note. A single conductor sensing a magnetic field connected to an indicator is included in the subject matter of this subclass type.

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323+,for geophysical surface or subsurface exploration which may include a moving coil magnetometer to detect objects below the surface of the earth or material within the earth or a magnetic field within the earth.

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33Geometrical Instruments,   subclass 361 for indicators of direction of force traversing natural media which use a rotating or vibrating magnetic detector.
343Communications: Radio Wave Antennas,   subclass 1 for radar devices which utilize a moving antenna, subclass 100 for directive radio systems that use a moving antenna, and subclass 757 for antennas with scanning, sweeping, or orienting means to move the antennas.
  
[List of Patents for class 324 subclass 258]    258Fixed coil-magnetometer:
 This subclass is indented under subclass 244.  Subject matter wherein the apparatus to sense a magnetic field is a stationary electrical coil placed in a changing magnetic field to be tested, and the apparatus to indicate the sensing of the field is connected to the coil whereby the changing magnetic field induces in the coil a voltage proportional to the number of turns of the coil and the time it takes the changing field to make a complete change.
(1) Note. The tested changing field may be the movement of a magnetic core in the magnetic field tested, the magnetic core being moved relative to the sensing coil.
(2) Note. The sensing coil may include a ferromagnetic core.
  
[List of Patents for class 324 subclass 259]    259Movable magnet or magnetic member interacts with magnetic field:
 This subclass is indented under subclass 244.  Subject matter with a movable permanent magnet acting as a magnetic field detector or a movable member of low magnetic reluctance acting as a magnetic field detector which includes material that can be temporarily magnetized by the tested field, the movable magnet"s magnetic field or the magnetic field of the temporarily magnetized material reacting to the tested magnetic field by moving until the force between the tested magnetic field and the movable magnet or the movable temporarily magnetized material is zero.
(1) Note. Magnetic polarity testers are here.

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205,for permanent magnet testing.
225,for test apparatus with compensation for a test variable.
256,for magnetometers having a movable energized coil which reacts with a tested magnetic field to indicate the direction or strength of the tested field.

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33Geometrical Instruments,   subclass 310 for borehole movable magnetic indicators for direction or inclination, subclass 319 for gyroscopically mounted magnetic compasses, subclass 352 for magnetic compass type directional indicators, and subclasses 355+ for magnetic compasses.
73Measuring and Testing,   subclasses 382+ for scales using permanent magnets to determine the force of gravity.
335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 205+ for permanent magnet actuated switches, and subclasses 302+ for magnets, per se.
  
[List of Patents for class 324 subclass 260]    260Magnetic field detection devices:
 This subclass is indented under subclass 200.  Subject matter which includes magnetic field sensing devices, per se, which are not classified elsewhere.

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213,for a magnetic recording medium placed on a magnetized test material which assumes the magnetization of the material and requires iron particles to visibly see the pattern of recording medium.
214,for paramagnetic particles placed in a tested magnetic field to note the pattern of the test field or on a magnetized test material to note the magnetization pattern of the magnetized material.
220+,for magnetic field sensing device and a support for the device to hold, position, or move the device in a pipe or borehole.
226,for apparatus involving a magnetic field detector combined with a diverse art device of another class.
228+,for means to create a magnetic test field and a magnetic sensor of the test magnetic field.
244+,for magnetometers which involve a magnetic sensor and an indicator responsive to the sensor.

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29Metal Working,   subclass 595 for indicating transducer making processes.
257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses, including subclasses 108 , 414, and 421-427, for devices responsive to magnetic field.
338Electrical Resistors,   subclasses 32+ for magnetic field or compass resistive devices including those of the Hall and superconductive type.
343Communications: Radio Wave Antennas,   subclasses 700+ for antennas.
360Dynamic Magnetic Information Storage or Retrieval,   subclasses 110+ for magnetic transducers, per se, used in dynamic magnetic information systems.
361Electricity: Electrical Systems and Devices,   subclasses 139+ , particularly subclasses 170+ for condition responsive control circuits for electromagnetic relay or solenoid devices, including subclasses 179+ for metal presence or absence devices.
365Static Information Storage and Retrieval,   for static magnetic information devices and the storage elements, per se, especially subclass 157 for magnetostrictive; and subclass 160 for superconductive information storage devices.
367Communication, Electrical: Acoustic Wave Systems and Devices,   subclasses 156 and 168 for underwater magnetostrictive transducers.
  
[List of Patents for class 324 subclass 261]    261With support for article:
 This subclass is indented under subclass 260.  Subject matter wherein material is to be examined magnetically by a magnetic field sensing device and structure is provided to hold the material with respect to the sensor so that the sensing can be performed.

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226,for testing material magneticallym and conveying the tested material to or from the test.
262,for supports for magnetic sensing devices.
756.01through 756.07 for support for device under test or test structure in electrical testing generally.

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248Supports,   subclasses 176+ for article stands, and subclasses 309+ for article brackets.
250Radiant Energy,   subclass 491.1 for means to align or position an object relative to a detector.
  
[List of Patents for class 324 subclass 262]    262Magnetic test structure elements:
 This subclass is indented under subclass 200.  Subject matter which includes supports for tested material and sensing devices, and other elements not provided for elsewhere.

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756.01through 756.07 for support for device under test or test structure in electrical testing generally.

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174Electricity: Conductors and Insulators,   particularly subclasses 32+ for anti-inductive structures.
248Supports,   for holding devices for materials, particularly subclasses 2+ for machinery supports.
  
[List of Patents for class 324 subclass 263]    263Current through test material forms test magnetic field:
 This subclass is indented under subclass 200.  Subject matter which includes an electric circuit including terminals to contact a material to be magnetically tested so that current through the material and the terminals create a magnetic field in the material for test purposes.
(1) Note. Demagnetization as well as magnetization can be claimed as long as the test material forms the test field.

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217+,for testing railroad rails by magnetizing the rail and sensing the magnetic field in the rail with or without an indication of the sensing.
228+,for magnetically testing material.

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335Electricity: Magnetically Operated Switches, Magnets, and Electromagnets,   subclasses 209+ for magnets and electromagnets, and subclass 284 for magnetizing and demagnetizing magnets and electromagnets.
336Inductor Devices,   subclasses 5+ for inductors, per se, which are impedance devices which produce a magnetic field when energized.
361Electricity: Electrical Systems and Devices,   subclasses 143+ for systems for magnetizing, demagnetizing, or controlling the magnetic field, and subclass 267 for demagnetizing systems and processes.
  
[List of Patents for class 324 subclass 300]    300PARTICLE PRECESSION RESONANCE:
 This subclass is indented under the class definition.  Subject matter relating to the measurement of the energy interchange between precessing atomic particles in a surrounding electromagnetic field.
(1) Note. The energy interchange may be characterized by a ratio between the mechanical angular momentum and the magnetic moment of an atomic system.
(2) Note. Precession is a change in the orientation of the axis of a rotating particle, the effect of which is to rotate this axis (axis of spin) about a line (axis of precession) perpendicular to its original direction and to the axis (axis of torque) of the moment producing the change.
(3) Note. Resonant frequency is the frequency at which a given system or object will respond with maximum amplitude when driven by an external sinusoidal force of constant amplitude.
  
[List of Patents for class 324 subclass 301]    301Using magnetometer:
 This subclass is indented under subclass 300.  Subject matter utilizing means to measure the effects of external magnetic fields upon the resonance of a host material in a controlled electromagnetic field.
(1) Note. Host material is a material in which the resonance properties have been determined under controlled magnetic field conditions.

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244+,for magnetometers, per se.
  
[List of Patents for class 324 subclass 302]    302To determine direction:
 This subclass is indented under subclass 301.  Subject matter wherein the magnetometer is used to determine the direction of an external magnetic field relative to the location of the magnetometer.
(1) Note. External is used to mean those magnetic fields external of the instrument being used.
  
[List of Patents for class 324 subclass 303]    303Using well logging device:
 This subclass is indented under subclass 300.  Subject matter in which earth subsurface materials are subjected to magnetic resonance measurement by using a well logging device to transport the components of the testing system to the location to be tested.

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346,for systems using magnetic means to determine the electrical characteristics of the subsurface.

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73Measuring and Testing,   subclasses 152.02+ for a process or an apparatus for well logging, per se, wherein the process or the apparatus is not purely electrical or purely magnetic.
  
[List of Patents for class 324 subclass 304]    304Using optical pumping or sensing device:
 This subclass is indented under subclass 300.  Subject matter in which a source of optical energy is applied to the sample and a resultant amount of optical energy is reradiated and sensed as a measure of a controlled interaction between the metastable state of an atomic system and a steady magnetic field.
(1) Note. Metastable is the marginal energy state of an electron above a reference ground within an atom, and having a definite lifetime.
  
[List of Patents for class 324 subclass 305]    305Having particular optical cell structure:
 This subclass is indented under subclass 304.  Subject matter wherein the optical cell is designed to aid the sensing of reradiated optical energy.
  
[List of Patents for class 324 subclass 306]    306Determine fluid flow rate:
 This subclass is indented under subclass 300.  Subject matter in which a fluid is magnetically tagged as a net magnetization in a predetermined direction at a tagging station for detection at a known distance downstream at a detection station within a measured time interval.
(1) Note. Magnetically tagged refers to the magnetic resonance of a fluid volume upon passage through a magnetic induction coil.

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73Measuring and Testing,   subclass 861.11 for electromagnetic induction-type volume or rate of flow meters.
116Signals and Indicators,   subclass 112 for fluid flow indicators.
600Surgery,   particularly subclass 419 for magnetic resonance imaging or spectroscopy of fluid flow limited to medically evaluating a body liquid or gas traveling through a living body and where structure particularly adapted for placement on or in the body is claimed.
  
[List of Patents for class 324 subclass 307]    307Using a nuclear resonance spectrometer system:
 This subclass is indented under subclass 300.  Subject matter in which a spectrometer is used to induce and measure resonance in the nucleus of an atom or group of atoms.
(1) Note. The spectrometer system would include at least a polarizing magnetic field element, a signal transmitter and receiver along with transducer coils coupled to a sample material being measured, and an indicator to readout information obtained.

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600Surgery,   particularly subclasses 410+ for a magnetic resonance imaging or spectroscopy device where structure particularly adapted for placement on or in a living body is claimed.
850Scanning-Probe Techniques or Apparatus; Applications of Scanning-Probe Techniques, e.g., Scanning-Probe Microscopy [SPM],   subclasses 46 through 49for magnetic force microscopy.
  
[List of Patents for class 324 subclass 308]    308Including a test sample and control sample:
 This subclass is indented under subclass 307.  Subject matter in which the nuclear resonance measurement of an unknown material is made by comparison with the resonance of a known material.
  
[List of Patents for class 324 subclass 309]    309To obtain localized resonance within a sample:
 This subclass is indented under subclass 307.  Subject matter in which a measurement of nuclear magnetic resonance at controlled locations within a sample volume is obtained.
  
[List of Patents for class 324 subclass 310]    310By scanning sample frequency spectrum:
 This subclass is indented under subclass 307.  Subject matter wherein the application of pulsed energy to an atom nucleus over a controlled range of frequencies results in relative energy absorption by the atom or atoms of a sample material at resonance.
(1) Note. Scanning may also take place as a result of an increase or decrease in magnetic field strength.
  
[List of Patents for class 324 subclass 311]    311With signal decoupling:
 This subclass is indented under subclass 307.  Subject matter in which feedback from the signal receiver to the transmitter is suppressed or eliminated.
(1) Note. The receiver feedback is not restricted to signals from the receiving coil and electronic components, but also includes the received and reradiated energy of the resonant sample material.
  
[List of Patents for class 324 subclass 312]    312By spectrum storage and analysis:
 This subclass is indented under subclass 307.  Subject matter wherein the nuclear resonant frequencies of the sample material are transformed to memory and recalled for computation.
(1) Note. Transformation may include the conversion of resonant frequency signal information from analog to digital form.
  
[List of Patents for class 324 subclass 313]    313Including polarizing magnetic field/radio frequency tuning:
 This subclass is indented under subclass 307.  Subject matter wherein the degree of resolution at resonance is a result of adjustment between magnetic field strength and the frequency at which magnetic resonance occurs.
  
[List of Patents for class 324 subclass 314]    314With conditioning of transmitter signal:
 This subclass is indented under subclass 307.  Subject matter in which the signal information applied to the sample to induce resonance is made to conform with the predetermined frequency or phase conditions of a transmitter.
(1) Note. The subject matter under frequency or phase control of a transmitted signal would involve an improvement in sample resonance resolution, sensitivity, stability, or possibly the removal of unwanted sidebands from a frequency system.
  
[List of Patents for class 324 subclass 315]    315With sample resonant frequency and temperature interdependence:
 This subclass is indented under subclass 307.  Subject matter in which the nuclear resonance of the sample material is measured as a function of temperature, or the temperature of the sample material is measured as a function of nuclear resonance.
  
[List of Patents for class 324 subclass 316]    316Using an electron resonance spectrometer system:
 This subclass is indented under subclass 300.  Subject matter in which a spectrometer is used to induce and measure electron resonance of a sample material.
(1) Note. The electrons of atoms of a sample material refers to the electrons of a single atom as well as electrons of bonded atoms.
(2) Note. A spectrometer system as used here would include at least a signal transmitter coupled to a microwave cavity in which a sample material is placed between the poles of a steady magnetic field and a receiver coupled to relay sample material resonance to an indicator.
  
[List of Patents for class 324 subclass 317]    317Including a test sample and control sample:
 This subclass is indented under subclass 316.  Subject matter wherein the electron resonance of an unknown material is made by comparison with the resonance of known material.
  
[List of Patents for class 324 subclass 318]    318Spectrometer components:
 This subclass is indented under subclass 300.  Subject matter comprising structural components of a spectrometer.

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600Surgery,   particularly subclass 419 for a magnetic resonance imaging or spectroscopy system component where structure particularly adapted for contacting or conforming to a body part of a patient is claimed.
  
[List of Patents for class 324 subclass 319]    319Polarizing field magnet:
 This subclass is indented under subclass 318.  Subject matter comprising the details of polarizing field magnet structure designed specifically for use with a spectrometer.
  
[List of Patents for class 324 subclass 320]    320With homogeneity control:
 This subclass is indented under subclass 319.  Subject matter where magnetic circuit component design permits a uniform magnetic field gradient to be obtained.
  
[List of Patents for class 324 subclass 321]    321Sample holder structure:
 This subclass is indented under subclass 318.  Subject matter comprising sample holders to be used specifically with a spectrometer.
  
[List of Patents for class 324 subclass 322]    322Electronic circuit elements:
 This subclass is indented under subclass 318.  Subject matter comprising basic circuit elements which include active and passive devices designed specifically for use in a spectrometer system.
  
[List of Patents for class 324 subclass 323]    323OF GEOPHYSICAL SURFACE OR SUBSURFACE IN SITU:
 This subclass is indented under the class definition.  Subject matter relating to the determination of an electrical characteristic of the subsurface of the earth in situ.
(1) Note. Subsurface is defined as including everything, whether composition, article, structure, or formation which lies below the upper natural surface of the earth. The upper surface is defined as being the uppermost nongaseous thing which lies on the earth, and may be mud, water, snow, leaves, dead trees, ice pavements, crops of buildings and such upper surface is defined as being natural if of the same type (e.g., leaves) which is found in nature, whether deposited by nature or not. Thus, under the subclass definition, the determination of geologic structure under building foundations or the location or treasure buried in the earth is included, but the location of treasure concealed in the building wall is not included.
(2) Note. The electrical characteristics which are determined may include streaming, telluric, terrestrial or self-potentials, resistance, dielectric constant, magnetic reluctance, inductance, conductance, capacitance, and magnetism.

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376,for the analysis of core samples, not in situ in the earth, and other appropriate subclasses for the analysis of samples which are not in situ, or for the location of objects which are not below the natural surface of the earth. Note particularly subclasses 67, 158, and 200+.

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23Chemistry: Physical Processes,   subclass 230 for geochemical exploration.
73Measuring and Testing,   subclasses 152.01+ for mechanical (e.g., thermal) analysis of bore holes.
166Wells,   subclasses 250+ for well processes including indicating, testing, or measuring steps; subclass 64 for well apparatus including time or distance measuring, temperature responsive or counting means; and subclass 66 for well apparatus including electrical indicating means.
175Boring or Penetrating the Earth,   subclass 40 and particularly subclass 50 for the combination of earth boring with electrical earth formation logging. The mere nominal recitation of a conventional earth boring step or means will not preclude classification in Class 324.
181Acoustics,   subclass .5 for nonelectrical geophysical exploration by the use of seismic waves. Also note the reference to Class 340 below.
250Radiant Energy,   subclasses 253+ for geophysical exploration by the use of radiant energy of the invisible type, including electromagnetic waves above the microwave frequency band.
340Communications: Electrical,   subclass 853.8 for a wellbore telemetering system.
343Communications: Radio Wave Antennas,   subclasses 5+ for radar systems which are used in geophysical exploration, as for example, radar sets which are lowered down a bore hole to determine the size of the bore.
367Communications, Electrical: Acoustic Wave Systems and Devices,   subclasses 14+ for seismic prospecting using electrical acoustic wave systems.
  
[List of Patents for class 324 subclass 324]    324Including borehole fluid investigation:
 This subclass is indented under subclass 323.  Subject matter relating to the determination of an electrical property of the fluid in a well, borehole, or other opening in the earth.
(1) Note. The fluid may be oil, gas, water, brine, or any other fluid.

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438,for determining the pH or conductivity of an electrolyte.

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73Measuring and Testing,   subclasses 152.18+ for fluid analysis in a borehole or drilling test wherein the analysis is not made by purely electrical or purely magnetic means.
204Chemistry: Electrical and Wave Energy,   subclasses 400+ as the residual home for apparatus used for electrolytic analysis or testing, per se.
205Electrolysis: Processes, Compositions Used Therein, and Methods of Preparing the Compositions,   subclasses 775+ as the residual home for a process of electrolytic analysis or testing, per se.
252Compositions,   subclass 62.2 for electrolytes of general utility.
  
[List of Patents for class 324 subclass 325]    325To determine fluid entry:
 This subclass is indented under subclass 324.  Subject matter relating to the determination of the subsurface location of the point or region of entry of a fluid into or out of a well, borehole, or other opening in the earth.

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73Measuring and Testing,   subclass 40.5 for the determination of the leakage or ingress of fluid from or into a conduit in situ and subclasses 152.18+ for a rate of fluid flow measuring or fluid analysis in a borehole or drilling test wherein the measurement or the analysis is not made by purely electrical means or purely magnetic means.
  
[List of Patents for class 324 subclass 326]    326For small object detection or location:
 This subclass is indented under subclass 323.  Subject matter relating to the detection or location in the earth of items which are relatively small compared to the size of the geoligic formation in which they are found.
(1) Note. The items may be objects such as land mines, unexploded shells, lost or buried treasure, pipes, etc.

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67,and 200+, for the detection of concealed objects, not below the natural surface of the earth, using magnetic or electromagnetic sensing, as the location of pipe in walls.
  
[List of Patents for class 324 subclass 327]    327Using oscillator coupled search head:
 This subclass is indented under subclass 326.  Subject matter wherein one or more parameters of an oscillator, coupled to or formed in conjunction with a coil or antenna moved over the region of exploration, are monitored.

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332,for subject matter under subclass 323 using a radiant energy transmitter.

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331Oscillators,   for a particular type of oscillator circuitry.
  
[List of Patents for class 324 subclass 328]    328Of the beat frequency type:
 This subclass is indented under subclass 327.  Subject matter having means for mixing the search head signal with another signal to produce a difference frequency output.

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331Oscillators,   subclasses 37+ for beat frequency oscillator circuits in general.
  
[List of Patents for class 324 subclass 329]    329Using movable transmitter and receiver:
 This subclass is indented under subclass 326.  Subject matter wherein an antenna or coil means for generating an electromagnetic field and a separate pickup coil or antenna means responsive to the electromagnetic field as modified by the object to be detected are transported simultaneously over the area of investigation.

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330,for transmitters and receiver combinations used in aerial surveys.
334,for transmitter-receiver systems for geophysical prospecting in general.

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455Telecommunications,   subclass 90.1 for portable transmitter-receiver systems having particular application.
  
[List of Patents for class 324 subclass 330]    330By aerial survey:
 This subclass is indented under subclass 323.  Subject matter in which the determination of the electrical property is made by means which are situated by a substantial distance above the earth"s surface.
(1) Note. The means may, for example, be carried by a projectile, rocket, aircraft, balloon, or may be supported on towers. The transportation of such means in a mere surface vehicle, such as an automobile, is not considered to be within the scope of this subclass.
  
[List of Patents for class 324 subclass 331]    331For magnetic field detection:
 This subclass is indented under subclass 330.  Subject matter having means for detecting a component of the earth"s magnetic field.

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345,for magnetic prospecting means in general.
  
[List of Patents for class 324 subclass 332]    332With radiant energy or nonconductive-type transmitter:
 This subclass is indented under subclass 323.  Subject matter having means for radiating electrostatic or electromagnetic energy into the earth and for measuring a circuit parameter of the radiating means.
(1) Note. The means for radiating the energy, for example, may be an oscillator search coil, and the reaction of the formation on the oscillator field, due to variable loading, may furnish the indication which is desired.

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327,for the measurement of oscillator circuit parameters in small object detection.
  
[List of Patents for class 324 subclass 333]    333Within a borehole:
 This subclass is indented under subclass 332.  Subject matter in which the transmitter is adapted for use within a drill hole in the earth.

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338,for borehole investigation with separate pickup of radiated energy.
346,for borehole investigation using magnetic means.
351,355 and 366+, for electrode arrangements used in a borehole.
  
[List of Patents for class 324 subclass 334]    334With separate pickup:
 This subclass is indented under subclass 332.  Subject matter having means distinct from the radiating means, for detecting the energy which has been radiated.
(1) Note. The earth, for example, may act as a mutual inductance to convey a variable amount of energy from a transmitter coil to a receiver coil, in dependence upon the electrical characteristics of the formation.

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329,for the detection of small objects using transmitter-receiver means.
330,for transmitter-receiver systems used in aerial surveys.

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455Telecommunications,   subclasses 39+ for particular transmitter-receiver systems used in communication.
  
[List of Patents for class 324 subclass 335]    335Employing multiple frequencies:
 This subclass is indented under subclass 334.  Subject matter in which more than one frequency is employed for investigating the subsurface formation between the transmitter and pickup.
(1) Note. The plurality of frequencies may be produced by varying the frequency of the signal from a single source, or, by provision of a plurality of different frequency sources.
  
[List of Patents for class 324 subclass 336]    336To detect transient signals:
 This subclass is indented under subclass 334.  Subject matter wherein the transmitter signal is such as to cause decaying secondary signals to emanate from subsurface ore bodies and mineral deposits and the pickup means detects such decaying secondary signals.

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360,for electrode systems which detect transient-type signals.
  
[List of Patents for class 324 subclass 337]    337To detect return wave signals:
 This subclass is indented under subclass 334.  Subject matter having the pickup means positioned at the same location as the transmitter for receiving reflections or reradiations of the transmitted signal.

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343Communications: Radio Wave Antennas,   subclasses 5+ for radar systems.
  
[List of Patents for class 324 subclass 338]    338Within a borehole:
 This subclass is indented under subclass 334.  Subject matter adapted for use within a drill hole in the earth.

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333,for measuring parameters of a radiant energy means positioned in the borehole.
346,for borehole investigation using magnetic means.
351+,355 and 366+, for electrode arrangements used in a borehole.
  
[List of Patents for class 324 subclass 339]    339By induction logging:
 This subclass is indented under subclass 338.  Subject matter in which eddy currents are induced in the formations surrounding the borehole by an alternating electromagnetic field from a transmitter coil and a secondary electromagnetic field set up by the eddy currents induces an electromotive force in the pickup or receiver coil.

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239+,for induced voltage-type sensors in magnetic testing.
  
[List of Patents for class 324 subclass 340]    340To measure susceptibility:
 This subclass is indented under subclass 339.  Subject matter relating to the measurement of magnetic properties of the formation.
  
[List of Patents for class 324 subclass 341]    341To measure dielectric constant:
 This subclass is indented under subclass 339.  Subject matter relating to the measurement of permittivity properties of the formation.
  
[List of Patents for class 324 subclass 342]    342Using a toroidal coil:
 This subclass is indented under subclass 339.  Subject matter in which one or both of the transmitter and pickup coils are in the configuration of a toroid.
  
[List of Patents for class 324 subclass 343]    343Using angularly spaced coils:
 This subclass is indented under subclass 339.  Subject matter in which the axis of one or more of the transmitter coils is nonparallel to the axis of one or more of the receiver coils.
  
[List of Patents for class 324 subclass 344]    344With radiant energy or nonconductive-type receiver:
 This subclass is indented under subclass 323.  Subject matter having means for receiving electrostatic or electromagnetic energy from above or below the surface of the earth.
(1) Note. The means, for example, may be responsive to radiant energy produced by natural sources but not by artificial sources. Receivers responsive to energy produced by an artificial source are classifiable elsewhere.

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332+,for this subject matter having transmitter means to radiate electrostatic or electromagnetic energy into the earth.
334,for receivers responsive to energy produced by an artificial source.
359,for a radiant energy pickup means responsive to radiant energy produced by artificial earth currents.
  
[List of Patents for class 324 subclass 345]    345By magnetic means:
 This subclass is indented under subclass 323.  Subject matter having magnetic means to determine the electrical characteristics of the subsurface.
(1) Note. For example, the magnetic field, due to artificial or natural earth current, may be determined.

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331,for determining the magnetic field by aerial survey.
  
[List of Patents for class 324 subclass 346]    346Within a borehole:
 This subclass is indented under subclass 345.  Subject matter adapted for use within a drill hole in the earth.

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303,for magnetic resonance measuring using well logging systems.
333,for measuring parameters of a radiant energy means positioned in the borehole.
338,for borehole investigation with separate pickup of radiant energy.
351,355 and 366+, for electrode arrangements used in a borehole.
  
[List of Patents for class 324 subclass 347]    347Using electrode arrays, circuits, structure, or supports:
 This subclass is indented under subclass 323.  Subject matter relating to means for introducing electric currents into the subsurface or for collecting electric currents from the subsurface by conduction.
(1) Note. This subclass includes the structure or configuration of one or more electrodes and the means for supporting such electrodes. The electrodes and their supports are primarily of the borehole type, although not limited thereto.

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437,445 through 449, for electrode structures and systems.

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128Surgery,   subclasses 2.06 and 2.1 for the structure of electrodes utilized in medical diagnosis, such as gelatin electrodes.
  
[List of Patents for class 324 subclass 348]    348For detecting naturally occurring fields, currents, or potentials:
 This subclass is indented under subclass 347.  Subject matter for measuring a field, current, or potential which exists as a result of the inherent nature of the subsurface formations and not arising by virtue of an artificial current source.
(1) Note. For purposes of this subclass naturally occurring fields, currents, or potentials are considered to include those resulting from such sources as electric powerlines, electrical machinery, and underground pipes. These sources are considered a permanent part of the environment.

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72,for detecting potentials in a specific environment.
  
[List of Patents for class 324 subclass 349]    349Of the telluric type:
 This subclass is indented under subclass 348.  Subject matter wherein the potentials or fields are associated with naturally occurring variable current which permanently circulate in vast sheets within the outermost layer of the earth"s crust.
  
[List of Patents for class 324 subclass 350]    350Including magneto-telluric type:
 This subclass is indented under subclass 349.  Subject matter for carrying out the telluric measurements in conjunction with measurements of the earth"s magnetic field.
  
[List of Patents for class 324 subclass 351]    351Within a borehole:
 This subclass is indented under subclass 348.  Subject matter adapted for use within a hole which has been drilled or is being drilled within the earth.

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333,for measuring parameters of a radiant energy means positioned in the borehole.
338+,for borehole investigation with separate pickup of radiated energy.
346,for borehole investigation using magnetic means.
355,for borehole electrodes coupled to an artificial current source.
366+,for separate pickup electrodes.
  
[List of Patents for class 324 subclass 352]    352Combined with artificial source measurement:
 This subclass is indented under subclass 351.  Subject matter including one or more additional types of electrode measurements employing a source of electrical energy other than a natural source.
(1) Note. The "additional" types of measurements include only those which would be classified within this class (324).
  
[List of Patents for class 324 subclass 353]    353With fluid movement or pressure variation:
 This subclass is indented under subclass 351.  Subject matter including means for causing the movement of the fluid or variations in the pressure of the fluid existing within the borehole or the formations surrounding the borehole.
  
[List of Patents for class 324 subclass 354]    354Coupled to artificial current source:
 This subclass is indented under subclass 347.  Subject matter in which a parameter of the current introduced into the subsurface is measured.
  
[List of Patents for class 324 subclass 355]    355Within a borehole:
 This subclass is indented under subclass 354.  Subject matter adapted for use within a drill hole in the earth.

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333,for measuring parameters of a radiant energy means positioned in the borehole.
338+,for borehole investigation with separate pickup of radiated energy.
346,for borehole investigation using magnetic means.
351+,for borehole electrode arrangements used in detecting naturally occurring fields and potentials.
366+,for borehole electrode arrangements with current emitting electrodes and separate potential pickup electrodes.

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73Measuring and Testing,   subclasses 152.01+ for an apparatus or a process for borehole testing, per se, wherein the test is not made by purely electrical means or by purely magnetic measuring means.
  
[List of Patents for class 324 subclass 356]    356While drilling:
 This subclass is indented under subclass 355.  Subject matter associated with a drill string so that measurements can be carried out during drilling of the borehole.

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368,for borehole logging while drilling devices having separate pickup means.

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73Measuring and Testing,   subclasses 152.03+ , 152.19+, and 152.43+ for an apparatus or a process for borehole testing during drilling, per se, wherein the test is not made by purely electrical means or by purely magnetic measuring means.
  
[List of Patents for class 324 subclass 357]    357Including separate pickup of generated fields or potentials:
 This subclass is indented under subclass 354.  Subject matter having means distinct from the current introduction means, for detecting the fields or potentials resulting from the current which has been caused to flow into the subsurface.

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64,for the detection of potentials caused by current flow in conducting resistance measurements in general.
  
[List of Patents for class 324 subclass 358]    358With three electrodes:
 This subclass is indented under subclass 357.  Subject matter having three potential pickup electrodes.
  
[List of Patents for class 324 subclass 359]    359With nonelectrode pickup means:
 This subclass is indented under subclass 357.  Subject matter having means for detecting radiant energy produced by the artificial current flow, including magnetic, electromagnetic, and electrostatic fields.
(1) Note. Subclass 345 takes precedence when detecting a magnetic field if the means for introducing the artificial current flow is not significant.
  
[List of Patents for class 324 subclass 360]    360Using a pulse-type current source:
 This subclass is indented under subclass 357.  Subject matter wherein the current introduced into the subsurface has an abruptly changing waveform such as a pulse, step impulse, square wave, etc.
(1) Note. The introduced current may include a single pulse-type signal or a plurality of such signals.
  
[List of Patents for class 324 subclass 361]    361With mechanical current reversing means:
 This subclass is indented under subclass 360.  Subject matter in which the current is caused to reverse direction by mechanical switching apparatus.
  
[List of Patents for class 324 subclass 362]    362To measure induced polarization:
 This subclass is indented under subclass 360.  Subject matter adapted to determine the polarization effects produced at the interface between a mineral body and a surrounding electrolyte in response to current flow.
  
[List of Patents for class 324 subclass 363]    363By varying the path of current flow:
 This subclass is indented under subclass 357.  Subject matter in which the current introduced is caused to travel through the subsurface formations over different paths.
  
[List of Patents for class 324 subclass 364]    364Using frequency variation:
 This subclass is indented under subclass 363.  Subject matter in which the current flow paths are varied by changing the frequency of the current.
  
[List of Patents for class 324 subclass 365]    365Offshore:
 This subclass is indented under subclass 357.  Subject matter adapted for use on or below the surface of a body of water.
  
[List of Patents for class 324 subclass 366]    366For well logging:
 This subclass is indented under subclass 357.  Subject matter adapted for use within a drill hole in the earth.

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333,for measuring parameters of a radiant energy means positioned in the borehole.
338,for borehole investigation with separate pickup of radiated-energy.
346,for borehole investigation using magnetic means.
351,for borehole electrode arrangements used in detecting naturally occurring fields and potentials.
355,for borehole electrodes coupled to an artificial current source.

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73Measuring and Testing,   subclasses 152.02+ for formation logging, per se, in a borehole or a drilling test wherein the measurement or the analysis is not made by purely electrical means or purely magnetic means.
  
[List of Patents for class 324 subclass 367]    367Using a pad member:
 This subclass is indented under subclass 366.  Subject matter in which the electrodes are mounted on the face of a support structure (pad member) adapted to extend into engagement with the borehole wall.

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374,for pad members used with focussing electrodes.
  
[List of Patents for class 324 subclass 368]    368Cased borehole:
 This subclass is indented under subclass 366.  Subject matter in which the drill hole to be investigated contains a metal sheath or casing.
  
[List of Patents for class 324 subclass 369]    369While drilling:
 This subclass is indented under subclass 366.  Subject matter associated with a drill string so that measurements can be carried out during drilling of the borehole.

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355,for borehole logging while drilling in which a parameter of current from an artificial current source is measured.

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73Measuring and Testing,   subclasses 152.03+ for formation logging, per se, in a borehole while drilling, and subclasses 152.19+ and 152.43+ for a borehole or drilling test while drilling wherein the measurement or the analysis is not made by purely electrical means or purely magnetic means.
  
[List of Patents for class 324 subclass 370]    370Using surface current electrodes:
 This subclass is indented under subclass 366.  Subject matter in which potentials detected along the borehole are created by current flowing between electrodes located at the earth"s surface on opposite sides of the borehole.
  
[List of Patents for class 324 subclass 371]    371Using plural fields:
 This subclass is indented under subclass 366.  Subject matter having means for creating more than one field in the formations surrounding the borehole and pickup electrode means responsive to each of the fields.
(1) Note. The fields may be created simultaneously or at different times and may have the same or different frequencies.
  
[List of Patents for class 324 subclass 372]    372Between spaced boreholes:
 This subclass is indented under subclass 366.  Subject matter in which electrode means are lowered within two or more drill holes in the earth for investigating the formations between the boreholes.
  
[List of Patents for class 324 subclass 373]    373Using current focussing means:
 This subclass is indented under subclass 366.  Subject matter in which main survey current and auxiliary guard current electrodes are provided so as to confine or "focus" the survey current to a thin horizontal path into the formations.
  
[List of Patents for class 324 subclass 374]    374Including pad member:
 This subclass is indented under subclass 373.  Subject matter in which the electrodes are mounted on the face of a support structure (pad member) adapted to extend into engagement with the borehole wall.

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367,for nonfocusing electrodes mounted on a pad member.
  
[List of Patents for class 324 subclass 375]    375Including plural current focussing arrays:
 This subclass is indented under subclass 373.  Subject matter having more than one focussing electrode configuration on a single borehole tool.
(1) Note. The plural configurations may include different focussing electrode systems such as an elongated array combined with a pad member array, a single type system with means for switching between electrodes to form the plural configurations, or separate arrays of the same type vertically spaced along the borehole. This subclass does not include a plurality of similar pad member arrays horizontally spaced around the borehole.
  
[List of Patents for class 324 subclass 376]    376OF SUBSURFACE CORE SAMPLE:
 This subclass is indented under the class definition.  Subject matter relating to the analysis by electrical means of core samples which have been removed from the subsurface of the earth.
(1) Note. For a definition of subsurface as used in these definitions see the definitions of subclass 323 of the class.

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323+,for this subject matter where the core sample is analyzed in situ in the earth.

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73Measuring and Testing,   subclasses 152.07 , 152.09, and 152.11 for logging a formation by a core sample analysis and subclasses 152.23+ for a fluid flow measuring or a fluid analysis in a borehole or drilling test combined with sampling wherein the measurement or the analysis is not made by purely electrical means or purely magnetic means.
175Boring or Penetrating the Earth,   subclass 44 providing core position identification for core sample orientation.
  
[List of Patents for class 324 subclass 377]    377For magnetic properties:
 This subclass is indented under subclass 376.  Subject matter wherein a magnetic property of the sample is analyzed.
(1) Note. For example, magnetic orientation, susceptance, permeability, dip and strike.
  
[List of Patents for class 324 subclass 378]    378INTERNAL-COMBUSTION ENGINE IGNITION SYSTEM OR DEVICE:
 This subclass is indented under the class definition.  Subject matter relating to the testing of electrical systems and devices which cause the rapid combustion of a fuel in an internal-combustion engine.
(1) Note. This subclass includes, for example, means for testing spark plugs, spark plug wires, coils, distributor points, magnetos, ignition timing, etc.

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73Measuring and Testing,   subclasses 114.62 through 114.67for measuring or testing the ignition system of an internal combustion engine and subclass 114.08 for using an ignition measurement for determining irregular combustion (e.g., misfire) using an ignition measurement.
123Internal-Combustion Engines,   subclass 146.5 for internal-combustion engine structure in combination with the ignition system under test.
  
[List of Patents for class 324 subclass 379]    379With analysis of displayed waveform:
 This subclass is indented under subclass 378.  Subject matter having a cathode-ray tube (CRT) display or a drive circuit for a CRT responsive to an electrical ignition system to display the waveform generated by the ignition system.

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394,for the use of a CRT in the testing of spark plugs in situ.
  
[List of Patents for class 324 subclass 380]    380Electronic ignition system:
 This subclass is indented under subclass 378.  Subject matter wherein the ignition system utilizes solid-state switching devices and electronic components.
(1) Note. These electronic components are, for example, transistors, zener diodes and oscillators.
  
[List of Patents for class 324 subclass 381]    381With magnetically controlled circuit:
 This subclass is indented under subclass 380.  Subject matter wherein a magnetically controlled circuit has no conventional distributor contact points but uses a magnetic impulse generator in lieu thereof to trigger the transistor through an amplifier unit.
  
[List of Patents for class 324 subclass 382]    382With capacitor discharge circuit:
 This subclass is indented under subclass 380.  Subject matter wherein conventional distributor breaker points, or a magnetic impulse generator in the distributor, charges a capacitor that generally discharges to the primary coil circuit.
  
[List of Patents for class 324 subclass 383]    383By simulating or substituting for a component under test:
 This subclass is indented under subclass 378.  Subject matter wherein the test is made by providing the test instrument with a standard, or ideal, component, or components, arranged to be connected into the ignition system under test for similar components therein and thereby indicate faulty components by eliminating the components which are not operating properly.
  
[List of Patents for class 324 subclass 384]    384Using plural tests in a conventional ignition system:
 This subclass is indented under subclass 378.  Subject matter wherein two or more diverse electrical components in an ignition system are tested.
  
[List of Patents for class 324 subclass 385]    385Distributor:
 This subclass is indented under subclass 378.  Subject matter including means for testing components in the primary and secondary circuits of the distributor.

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421+,for contact resistance test.
  
[List of Patents for class 324 subclass 386]    386Dwell (i.e., cam angle):
 This subclass is indented under subclass 385.  Subject matter wherein the number of degrees the distributor cam rotates from the time the breaker points close until they open again is measured.
(1) Note. This subclass includes instruments which measure both dwell and revolutions per minute.

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160+,for electrical speed measuring.
  
[List of Patents for class 324 subclass 387]    387Condenser:
 This subclass is indented under subclass 385.  Subject matter for testing the operation of the energy storing component in the primary circuit of the ignition system.

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60+,for measuring capacitance.
  
[List of Patents for class 324 subclass 388]    388Coil:
 This subclass is indented under subclass 378.  Subject matter including means for testing the operation of the voltage transformer of the ignition circuit.

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59,for measuring inductance.
  
[List of Patents for class 324 subclass 389]    389Magneto:
 This subclass is indented under subclass 378.  Subject matter including means for testing the operation of the magnetic pulse generator of the ignition circuit.
  
[List of Patents for class 324 subclass 390]    390Low or high tension lead:
 This subclass is indented under subclass 378.  Subject matter including means for testing the electrical condition of the wires in the primary or secondary circuit of the ignition system.

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51,for fault testing and circuit continuity.
54,for insulation testing.
62,for measuring resistance or conductivity.
  
[List of Patents for class 324 subclass 391]    391Ignition timing:
 This subclass is indented under subclass 378.  Subject matter including means for measuring the time when a high voltage surge is provided to fire a spark plug for a particular cylinder relative to the position of the piston in the cylinder.

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73Measuring and Testing,   subclasses 114.62 through 114.67for measuring or testing the ignition system of an internal combustion engine, especially subclasses 114.63 - 114.66 for ignition timing testing and measurement and subclass 114.08 for using an ignition measurement for determining irregular combustion (e.g., misfire) using an ignition measurement.
  
[List of Patents for class 324 subclass 392]    392Using a pulse signal technique:
 This subclass is indented under subclass 391.  Subject matter wherein the timing measurement is achieved by using pulse signal processing (e.g., digital processing).
  
[List of Patents for class 324 subclass 393]    393In situ testing of spark plug:
 This subclass is indented under subclass 378.  Subject matter wherein the spark plug is tested while in the engine.

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403+,for testing of discharge characteristics of space discharge devices including spark plugs.
  
[List of Patents for class 324 subclass 394]    394With cathode-ray tube display:
 This subclass is indented under subclass 393.  Subject matter having a cathode-ray tube (CRT) display or a drive circuit for a CRT responsive to an electrical ignition system to display the waveform generated by the ignition system.

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379,for the general use of a CRT in the testing of internal-combustion engine ignition systems.
  
[List of Patents for class 324 subclass 395]    395Using an illuminating device to indicate spark plug condition:
 This subclass is indented under subclass 393.  Subject matter wherein a glow device (e.g., lamp bulb, neon tube, etc.) indicates whether or not a spark plug is operating properly.
  
[List of Patents for class 324 subclass 396]    396With an air gap in series with spark plug to indicate spark plug condition:
 This subclass is indented under subclass 393.  Subject matter having the air gap connected in series with the spark plug secondary circuit to give an indication of the condition of the spark plug.
  
[List of Patents for class 324 subclass 397]    397By shorting the plug to ground to indicate spark plug condition:
 This subclass is indented under subclass 393.  Subject matter wherein the test to indicate the condition of a spark plug consists of shorting the plug to ground and observing the change in the speed of the engine.
  
[List of Patents for class 324 subclass 398]    398With air gap in ground circuit:
 This subclass is indented under subclass 397.  Subject matter having the air gap connected in parallel with the spark plug circuit.
  
[List of Patents for class 324 subclass 399]    399Wherein a measured electric quantity indicates spark plug condition:
 This subclass is indented under subclass 393.  Subject matter wherein an electric characteristic (e.g., current, voltage, resistance, etc.) is evaluated or measured to indicate whether or not a spark plug is operating properly.
  
[List of Patents for class 324 subclass 400]    400Spark plug removed or tested in a test fixture:
 This subclass is indented under subclass 378.  Subject matter wherein the spark plug is removed from the engine or placed in a test fixture to determine the condition of the plug.
  
[List of Patents for class 324 subclass 401]    401Using a pressure chamber:
 This subclass is indented under subclass 400.  Subject matter wherein the test fixture has a means for testing the plug under pressure.
  
[List of Patents for class 324 subclass 402]    402Apparatus for coupling a measuring instrument to an ignition system:
 This subclass is indented under subclass 378.  Subject matter relating to devices which pick up signals from the ignition system and apply them to an analyzer.
  
[List of Patents for class 324 subclass 403]    403ELECTRIC LAMP OR DISCHARGE DEVICE:
 This subclass is indented under the class definition.  Subject matter comprising systems, apparatus, and methods for testing the operativeness or characteristics of electric lamps or electric discharge devices.
(1) Note. This subclass includes, for example, systems for determining the lumen output per watt of input for electric lamps.

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57+,for the measurement of the resistance of lamp filaments as long as the claims are not limited to the filaments being mounted in the lamp. These subclasses (20) provide for electrical systems for testing the characteristics of incandescent lamps, including the testing of the resistance of the filament within the lamp.
378+,for this subject matter utilized to test spark plugs or ignition systems.

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209Classifying, Separating, and Assorting Solids,   appropriate subclasses for methods and apparatus for automatically separating and assorting, or segregating in grades or classes according to physical characteristics, lamps, and space discharge devices.
315Electric Lamp and Discharge Devices: Systems,   subclasses 120 and 129+ for systems for operating an electric lamp and/or discharge device, the systems including signal, indicator, or alarm means to indicate some condition affecting the operation of the lamp or discharge device.
356Optics: Measuring and Testing,   subclasses 121+ for lamp beam direction or pattern tests with or without focussing of the lamp; subclass 123 for tests to determine the position of a filament with respect to its optical system; and subclasses 213+ for photometers.
445Electric Lamp or Space Discharge Component or Device Manufacturing,   subclasses 3+ for processes; and subclasses 63+ for apparatus for the manufacture of electric lamps or discharge devices which include an operation of testing or means to test the operativeness of the lamp or discharge device.
455Telecommunications,   appropriate subclasses for miscellaneous apparatus and systems for testing radio circuits.
  
[List of Patents for class 324 subclass 404]    404Cathode-ray tube:
 This subclass is indented under subclass 403.  Subject matter for testing a discharge device which has means for forming the electric discharge into a restricted beam or ray.
  
[List of Patents for class 324 subclass 405]    405Vacuum tube:
 This subclass is indented under subclass 403.  Subject matter for testing a device which is intended to have an electrical current flow between two spaced electrodes, at least part of the path followed by the discharge being constituted by a gas, vapor, or vacuum.
  
[List of Patents for class 324 subclass 406]    406Plural tubes in the testing circuit:
 This subclass is indented under subclass 405.  Subject matter having a plurality of vacuum tubes connected in the testing circuit during the testing operation.

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315Electric Lamp and Discharge Devices: Systems,   subclass 130 for miscellaneous plural load device systems having means to indicate a condition affecting the operation of one or more of the lamps and/or discharge devices; and subclasses 312+ and the subclasses specified in the notes to the definitions of these subclasses for miscellaneous systems for supplying electric energy to a plurality of lamps and/or discharge devices.
  
[List of Patents for class 324 subclass 407]    407Testing circuit for diverse-type tube:
 This subclass is indented under subclass 405.  Subject matter wherein the testing system or apparatus is provided with means so that two or more types of vacuum tubes may be tested by the same apparatus or system.

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315Electric Lamp and Discharge Devices: Systems,   subclasses 178+ and the subclasses specified in the notes to the definitions of these subclasses for miscellaneous systems for operating a plurality of diverse-type load devices.
  
[List of Patents for class 324 subclass 408]    408Circuit for making diverse test:
 This subclass is indented under subclass 405.  Subject matter wherein the testing circuit or apparatus is designed to test a plurality of different characteristics of conditions of vacuum tubes under examination.
(1) Note. Making a plurality of tests for short circuits between different electrodes is considered to be plural diverse testing for this subclass.

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407,wherein the method, apparatus, or testing circuit is designed for use with vacuum tubes of different types.
  
[List of Patents for class 324 subclass 409]    409Testing discharge space characteristic (e.g., emission):
 This subclass is indented under subclass 405.  Subject matter wherein the testing circuit or apparatus is designed to test the condition between two or more of the discharge electrodes of an electric discharge device, or is designed to test the characteristics of the interelectrode discharge space of a discharge device.
(1) Note. These subclasses including testing for short circuits between the electrodes of the discharge device and also deriving an operating characteristic of the discharge device such as the mutual conductance, amplification factor, etc. The testing of the impedance characteristic between one pair of electrodes is not deemed diverse type testing merely because that characteristic may be either normal or abnormal though short circuiting.

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408,for apparatus, systems, and methods for making a plurality of different tests.
  
[List of Patents for class 324 subclass 410]    410With application of current or potential to the discharge control means:
 This subclass is indented under subclass 409.  Subject matter wherein the circuit used in making the test includes means to impress current or potential upon the discharge control means of a vacuum tube.
  
[List of Patents for class 324 subclass 411]    411Pulsating or alternating current or potential for the discharge control means:
 This subclass is indented under subclass 410.  Subject matter wherein the current or potential impressed upon the discharge control means is pulsating or alternating current or potential.
  
[List of Patents for class 324 subclass 412]    412Pulsating or alternating current for the anode:
 This subclass is indented under subclass 411.  Subject matter wherein the circuit used in making the test includes means to impress pulsating or alternating current or potential upon the anode of the vacuum tube.
  
[List of Patents for class 324 subclass 413]    413Shock testing:
 This subclass is indented under subclass 405.  Subject matter in which the internal components of the vacuum tube are tested for mechanical vibration by striking the tube envelope with a hammer element.
  
[List of Patents for class 324 subclass 414]    414Electric lamp:
 This subclass is indented under subclass 403.  Subject matter for testing a device which converts electrical energy into visible light or ultraviolet light.
  
[List of Patents for class 324 subclass 415]    415ELECTROMECHANICAL SWITCHING DEVICE:
 This subclass is indented under the class definition.  Subject matter relating to the testing of operational characteristics of electromechanical devices which open and close or change the connection of a circuit.

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340Communications: Electrical,   subclasses 635+ for monitoring the condition of electrical apparatus.
  
[List of Patents for class 324 subclass 416]    416Voltage regulator:
 This subclass is indented under subclass 415.  Subject matter which includes determining the electrical properties of an electromechanical device which maintains a load voltage nearly constant over a range of variations of input voltage and load current.
  
[List of Patents for class 324 subclass 417]    417Thermostat switch:
 This subclass is indented under subclass 415.  Subject matter wherein the device under test consists of a temperature responsive circuit element which transforms temperature change to a change in the open or closed state of mating electrical contact surfaces.
  
[List of Patents for class 324 subclass 418]    418Relay:
 This subclass is indented under subclass 415.  Subject matter wherein the device under test consists of a switch contact member actuated by an electromagnet acting against a spring biased member to open or close switch contact surfaces.
  
[List of Patents for class 324 subclass 419]    419Reed switch:
 This subclass is indented under subclass 418.  Subject matter in which the relay to be tested is of the reed switch type.
  
[List of Patents for class 324 subclass 420]    420To evaluate contact chatter:
 This subclass is indented under subclass 418.  Subject matter wherein the resonant frequency at which the relay contact surfaces make and break a circuit is determined.
  
[List of Patents for class 324 subclass 421]    421To evaluate contact resistance:
 This subclass is indented under subclass 418.  Subject matter in which the magnitude of resistance to current flow across mating contact surfaces is determined.
  
[List of Patents for class 324 subclass 422]    422To evaluate contact sequence of operation:
 This subclass is indented under subclass 418.  Subject matter in which the order of make and break operation of plural contacts is determined.
  
[List of Patents for class 324 subclass 423]    423To evaluate contact response time:
 This subclass is indented under subclass 418.  Subject matter in which the rate of time resulting from contact separation as well as closure is determined.
  
[List of Patents for class 324 subclass 424]    424Circuit breaker:
 This subclass is indented under subclass 415.  Subject matter in which the electrical properties inherent to contacts separating in a high voltage-high current circuit are determined.
  
[List of Patents for class 324 subclass 425]    425ELECTROLYTE PROPERTIES:
 This subclass is indented under the class definition.  Subject matter for testing the electrolyte of electrolytic devices, or having electrolytic means for performing the testing to determine specific electrical properties of the electrolyte.

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204Chemistry: Electrical and Wave Energy,   subclasses 400+ as the residual home for apparatus used for electrolytic analysis or testing, per se.
205Electrolysis: Processes, Compositions Used Therein, and Methods of Preparing the Compositions,   subclasses 775+ as the residual home for a process of electrolyltic analysis or testing, per se.
  
[List of Patents for class 324 subclass 426]    426Using a battery testing device:
 This subclass is indented under subclass 425.  Subject matter in which the testing device used is specifically designed to test the condition of or properties of a battery.
(1) Note. This subclass contains, for example, means for testing the conditions of dry cells by means which measure terminal voltage under load.

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76+,