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 [Search a list of Patent Appplications for class 455]   CLASS 455,TELECOMMUNICATIONS
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SECTION I - CLASS DEFINITION

This is the generic class for modulated carrier wave communications not elsewhere classifiable.

Some art areas excluded from this class are: Alternating or pulsating current telegraphy; Antennas; Broadcast or multiplex stereo; Condition responsive indicating systems with a radio coupling link; Directive carrier wave systems; Multiplex carrier wave communications; Paging via modulated carrier wave; Pulse or digital communications which may be modulated onto a carrier wave; Reflected carrier wave systems (e.g., radar); Selective (e.g., remote control); Telemarketing; Television; Facsimile. (See References to Other Classes, below, for class references.)

SECTION II - LINES WITH OTHER CLASSES AND WITHIN THIS CLASS

The combination of the subject matter of this class (455) and other art environment is generally classified with the other art environment where that environment is significant by virtue of the claimed relationship. For example: Directive systems; Geophysical systems; Radar systems; Radio remote control systems; Telegraph systems; Telemetering systems; Television systems; Facsimile systems (See References to Other Classes, below.)

Subcombinations specific to a modulated carrier wave communication system are classified herein unless classified elsewhere. For example: Demodulation and detector, oscillators, per se, Modulators, per se, and tuners, per se, are classified elsewhere. (See References to Other Classes, below.)

(1) Note. The classification lines between this class (455) and the related subcombinations classes are found in the class definitions of these subcombination classes.

ORGANIZATION OF THIS CLASS

Subclasses 1-355 of this class (455) are limited to radio wave communication systems in which the carrier wave is modulated by a continuous (analog) signals. These subclasses exclude:

(A) Remote control of an external device which is classified in Class 340, subclasses 1.1-16.1.

(B) Multiplexing of signals which represent intelligence; see Class 370.

(C) Pulse or digital signals which represent intelligence; see Class 375.

The above subclasses may include pulse signals which are used to control a transmitter or receiver; however, where the information content is represented by a pulse or digital signal, classification is in Class 375. Subclass 899 of this class (455) is miscellaneous analog or pulse modulation carrier wave communication not elsewhere classified, for example, modulated protons, muons, or neutrino particles utilized for communication of information.

SECTION III - REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:

33Geometrical Instruments,   for geometrical type measuring instruments that may employ carrier wave telemetering links.
73Measuring and Testing,   which class may include carrier wave telemetric links.
178Telegraphy,   subclasses 66.1+ for alternating or pulsating current telegraphy. (See Lines With Other Classes and Within This Class, Art Areas Excluded From This Class.)
178Telegraphy,   for telegraph systems. (See Lines With Other Classes and Within This Class, Combination of The Subject Matter of This Class (455) and Other Art Environment.)
178Telegraphy,   provides in subclasses 2+ for various telegraph systems comprising means for transmitting mark and space or coded telegraph messages between stations and including a plurality of telegraph instruments, such as transmitting and receiving instruments in circuit, and indented subclass 49 for superimposed current systems.
246Railway Switches and Signals,   appropriate subclasses for carrier wave railway signalling systems, particularly subclasses 2+ for train dispatching systems; indented subclasses 7+ providing for telegraphy or telephony; subclasses 20+ for block-signal systems; and subclasses 167+ for cab signal or train control systems.
257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses for integrated circuit structure, bipolar, and field effect transistors (or combinations thereof), light emitting injection diodes, and other light emitting devices, etc.
330Amplifiers,   for demodulation and detector, per se.
331Oscillators,   for oscillators, per se.
332Modulators,   for modulators, per se.
334Tuners,   for tuners, per se.
340Communications: Electrical,   subclasses 1.1 through 16.1 for means for controlling the operations of a signaling device or devices in a selective manner over a lesser number of communication lines than the number of different results which can be obtained by signaling over said lines and which may contain transmission and receiving means in circuit (radio remote control systems), especially subclasses 12.5 and 12.51 for a radio link in pulse responsive selection actuation and subclasses 13.25 and 13.26 for radio link in frequency responsive actuation; subclasses 7.1-7.63 for paging via modulated carrier wave; subclass 311.2 for nonselective paging; subclasses 539.1-539.32 for condition responsive indicating systems with a radio coupling link; and subclasses 870.01-870.44 for telemetering systems in which the received signal is at any instant proportional to a condition at the transmitter.
342Communications: Directive Radio Wave Ssytems and Devices (e.g., Radar, Radio Navigation),   subclasses 350+ for directive carrier wave systems.
343Communications: Radio Wave Antennas,   subclasses 5+ for reflected carrier wave systems (e.g., radar); subclasses 100+ for directive radio wave systems; subclasses 700+ for antennas.
348Television,   for television systems.
358Facsimile and Static Presentation Processing,   for facsimile systems.
367Communications, Electrical: Acoustic Wave Systems and Devices,   for geophysical systems, for signalling by means of mechanical or compressional waves, such as sound or supersonic waves. See subclasses 87+ for echo systems; and subclasses 131+ for underwater systems.
370Multiplex Communications,   for multiplex communication systems which may include modulated carrier wave systems.
375Pulse or Digital Communications,   is the generic class for pulses modulated onto a nonlight wave carrier; see subclasses 222+ , 259+, 301, 303, 321, 322+, and 338+.
379Telephonic Communications,   for a two-way electrical transmission of intelligible audio information over an electrical conductor.
380Cryptography,   subclasses 255 through 276for a communication system using cryptography.
381Electrical Audio Signal Processing Systems and Devices,   subclasses 1+ for broadcast or multiplex stereo.
398Optical Communications,   various subclasses for optical communication.
399Electrophotography,   subclass 8 for remote monitoring of an electrophotographic device.
463Amusement Devices: Games,   subclasses 1+ , especially subclasses 39 and 40+, for a nonprojectile game with telecommunication means.
505Superconductor Technology: Apparatus, Material, Process,   subclasses 150+ for high temperature (Tc 30 K) superconducting devices, particularly subclasses 202+ for electrical communication systems.
709Electrical Computers and Digital Processing Systems: Multicomputer Data Transferring,   subclasses 200+ for data transferring among a plurality of spatially distributed computers or digital data processing systems.
714Error Detection/Correction and Fault Detection/Recovery,   appropriate subclasses for generic error checking.

SECTION IV - GLOSSARY

MODULATED CARRIER WAVE

A wave resulting when the necessary characteristics of an intelligence or information signal are impressed on a carrier wave.

RADIOTELEPHONE SYSTEM

A system for establishing a voice communication link between a base and a mobile transceiver via a wireless carrier wave channel that is allocated for use during a communication link, and wherein the mobile transceiver has a specific assigned call address number.

TELECOMMUNICATIONS

All types of communications systems in which electric or electromagnetic signals are used to transmit modulated carrier wave information between points. The transmission media is via radio wave generally of a frequency above human speech, yet at a frequency lower than infrared frequencies. Radiotelephonic communication via wireless link is included in this class.

SUBCLASSES

[List of Patents for class 455 subclass 1]    1INTERFERENCE SIGNAL TRANSMISSION (E.G., JAMMING):
 This subclass is indented under the class definition.  Subject matter including means to transmit an interference signal to interfere with a selected signal so as to prevent the intelligible reception of the selected signal.
(1) Note. The combination of an interference transmitter with a receiver to select the frequency of the incoming signal it is desired to jam or block, and control means to tune the transmitter to said frequency, is classified in this subclass when the receiver serves solely to determine the frequency of the incoming signal and to control the transmitter. If the receiver portion of the combination is complete (reproduces the intelligence received) the combination is a transceiver and is classified in this class (455), subclasses 73+.
(2) Note. Antijamming devices or methods are not classified here, but are found in subclasses 296+.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclass 18 for jamming or radar transmissions.
380Cryptography,   subclasses 252 through 254for concealment of information by masking of an information bearing signal.
  
[List of Patents for class 455 subclass 2.01]    2.01AUDIENCE SURVEY OR PROGRAM DISTRIBUTION USE ACCOUNTING:
 This subclass is indented under the class definition.  Subject matter including means for indicating, metering, or recording the number of receivers using a radio program, the length of time that a radio program is being used, which of several radio programs is being used, or which radio programs have been broadcast.
(1) Note. This subclass is provided for generic devices of this type. Use survey and accounting systems which are designed for a specific type of signal such as television are not classified here but in the class appropriate thereto.

SEE OR SEARCH THIS CLASS, SUBCLASS:

3.01+,for wireless program distribution systems.
26.1,for systems to prevent unauthorized use of a signal.

SEE OR SEARCH CLASS:

380Cryptography,   appropriate subclasses for a cryptographic system to prevent unauthorized use of a signal.
725Interactive Video Distribution Systems,   subclasses 1 through 8for billing in a video distribution system and subclasses 9-24 for surveying of receiver use, commercial or program airing verification, and awarding coupon, token, or credit, respectively.
  
[List of Patents for class 455 subclass 3.01]    3.01WIRELESS DISTRIBUTION SYSTEM:
 This subclass is indented under the class definition.  Subject matter including an organized arrangement of transmission links for connecting a plurality of discrete subscribers to a source of information signals.
(1) Note. This subclass and its indents are intended to collect devices, such as community antennas (inclusive of wireless local loop or WLL) and national or global networks.
(2) Note. Distribution systems including WLL which emphasize a specific type of signal such as television or digital are not classified here but rather in the appropriate class thereto.
(3) Note. Police, fire, and other radiotelephone systems which may include some elements of a distribution system are classified elsewhere. See the search notes below.

SEE OR SEARCH THIS CLASS, SUBCLASS:

3.05,for two-way wireless local loop.
132,for plural receivers.
149,for a plural output receiver.
272,for plural separate wave collectors combined with a receiver.
500through 528 and 59-72, for plural transmitters or receivers at separated stations (e.g., police, fire, and other radiotelephone systems which may include some elements of a distribution system).

SEE OR SEARCH CLASS:

307Electrical Transmission or Interconnection Systems,   subclasses 11 through 87for like systems without limitation of radiant energy path or analog carrier wave.
315Electric Lamp and Discharge Devices: Systems,   subclasses 39 and 39.3 for like systems with discharge devices.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 365 through 508for miscellaneous gating systems.
333Wave Transmission Lines and Networks,   subclasses 1 through 137for plural channel systems.
340Communications: Electrical,   subclasses 1.1 through 16.1for selective systems with distribution characteristics.
343Communications: Radio Wave Antennas,   subclasses 850 through 865for an antenna, per se, with coupling network.
375Pulse or Digital Communications,   appropriate subclasses for distribution systems designed for a specific type of digital signal.
725Interactive Video Distribution Systems,   for appropriate subclasses.
  
[List of Patents for class 455 subclass 3.02]    3.02Receiver for satellite broadcast:
 This subclass is indented under subclass 3.01.  Subject matter including an antenna for receiving satellite transmissions.
  
[List of Patents for class 455 subclass 3.03]    3.03Remote control of distribution:
 This subclass is indented under subclass 3.01.  Subject matter wherein some functions of a modulated carrier wave source or receiver are supervised or controlled from a remote site.
(1) Note. Because of a search note in subclass 3.05, only disclosures of more than mere control in the second directions should be cross referenced thereto.

SEE OR SEARCH THIS CLASS, SUBCLASS:

8,for repeater system with failure compensation.
26.1,for unauthorized use prevention systems.
31.1through 38.5, for systems with additional selectively responsive means.
68through 72, for control of communication system.
88,for transceiver controlling a separate transceiver or receiver.
92,for remote control of a transmitter.
132,for plural receivers of which one controls another.
352through 355, for remote control of a receiver.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 12.5 and 13.24 for remote control over a radio link.
380Cryptography,   appropriate subclasses for a cryptographic system to prevent unauthorized use of a signal.
  
[List of Patents for class 455 subclass 3.04]    3.04With subscriber selection or switching:
 This subclass is indented under subclass 3.03.  Subject matter including means for a subscriber to selectively receive desired information signals.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 1.1 through 16.1for generic selective systems.
  
[List of Patents for class 455 subclass 3.05]    3.05Two-way:
 This subclass is indented under subclass 3.01.  Subject matter including means for establishing communication in both directions.
(1) Note. Wherein the second communication is the notation or reporting of the program watched or listened to, classification is in audience survey and use accounting.
(2) Note. Wherein any communication in a system is in pulse form, such system is classified elsewhere. See the search notes below.
(3) Note. Wherein any communication in a system is in the form of light waves, such system is classified elsewhere.

SEE OR SEARCH THIS CLASS, SUBCLASS:

2.01,for audience survey and use accounting.

SEE OR SEARCH CLASS:

359Optical: Systems and Elements,   subclasses 109 through 195for an information signal transmitted between an optical transmitter and optical receiver by means of variation in a characteristic of light waves.
375Pulse or Digital Communications,   for communication in a system in pulse form.
  
[List of Patents for class 455 subclass 3.06]    3.06Combined with diverse art device (e.g., audio/sound or entertainment system):
 This subclass is indented under subclass 3.01.  Subject matter wherein the distribution system is combined with another art device.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclass 4.37 for selective program control of audio system and subclass 4.4 for selective control of audio system by pulse signal.
381Electrical Audio Signal Processing Systems and Devices,   subclasses 2 through 18for stereo broadcasting and subclasses 77-85 for one-way audio signal program distribution.
  
[List of Patents for class 455 subclass 7]    7CARRIER WAVE REPEATER OR REPLAY SYSTEM (I.E., RETRANSMISSION OF SAME INFORMATION):
 This subclass is indented under the class definition.  Subject matter comprising means whereby a radiant energy signal wave is received and reradiated at the same or different carrier frequency and usually at a higher energy level and/or in a desired direction.
(1) Note. Where the transmitted signal has a different characteristic than the received signal or involves the addition or subtraction of information classification is not in this subclass, but in Class 343 (see notes under subclass 6.5 in the class definition of Class 343). However, if the transmitted signal is on a different carrier frequency from the received signal merely to avoid interference classification is in this subclass.

SEE OR SEARCH CLASS:

178Telegraphy,   subclasses 70+ for repeaters specific to telegraphy.
330Amplifiers,   for amplifiers systems in general, particularly subclass 10 for modulator-demodulator type amplifiers for amplifying direct current or slowly varying alternating current signals.
332Modulators,   particularly subclasses 183+ for modulation converters for converting one modulated wave to a differently modulated wave (e.g., pulse modulation to frequency modulation or frequency modulation to amplitude modulation); subclass 108 for plural stage modulation systems wherein each stage is of the same or diverse type of modulation, the last stage being of the pulse modulation type; subclasses 119+ or 145, for plural stage modulation systems wherein the last stage is of the phase or frequency modulation type; and subclasses 151+ for plural stage modulation systems wherein the last stage is of the amplitude modulation type.
333Wave Transmission Lines and Networks,   subclass 117 for hybrid-type networks.
340Communications: Electrical,   subclass 291 for signal box repeaters which repeat, for example, signals received at a central station to a plurality of fire houses.
343Communications: Radio Wave Antennas,   subclasses 5+ for systems and apparatus which include a receiver-transmitter station designed for control by a wave transmitted from a first transmission station and designed to transmit a signal which is different from the received signal, i.e., adds additional information, the system including means to receive the signal transmitted by the receiver transmitter station. Where the signal which is transmitted by the receiver-transmitter is of the same character as the received signal, even though a time-delay is interposed between the time of reception and the time of transmission, the patent is classified in this subclass.
370Multiplex Communications,   subclasses 274 , 279, 293, 315+, and 492+ for repeaters using multiplex frequency channels.
  
[List of Patents for class 455 subclass 8]    8Failure compensation (e.g., spare channel):
 This subclass is indented under subclass 7.  Subject matter including apparatus for compensating for failure in operation of a repeater station.
  
[List of Patents for class 455 subclass 9]    9Monitoring:
 This subclass is indented under subclass 7.  Subject matter including means for measuring or testing the operating condition at a repeater station.
  
[List of Patents for class 455 subclass 10]    10Fading compensation:
 This subclass is indented under subclass 9.  Subject matter where the measured quantity is the strength of the received signal and variations in said received signal strength are compensated for.
  
[List of Patents for class 455 subclass 11.1]    11.1Portable or mobile repeater:
 This subclass is indented under subclass 7.  Subject matter wherein a receiving or transmitting station is not permanently mounted in one location, but is either carried by a person or associated with a movable object, such as a vehicle (i.e., mobile repeater station).
  
[List of Patents for class 455 subclass 12.1]    12.1Space satellite:
 This subclass is indented under subclass 11.1.  Subject matter wherein the repeater or relay is associated with an artificial satellite orbiting the earth.

SEE OR SEARCH CLASS:

342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 352+ which include a satellite.
343Communications: Radio Wave Antennas,   digest 2 for satellite mounted antenna.
370Multiplex Communications,   subclasses 316+ for a space satellite repeater using communication techniques.
  
[List of Patents for class 455 subclass 13.1]    13.1With plural repeater or relay systems:
 This subclass is indented under subclass 12.1.  Subject matter having more than one modulated carrier wave and having a repeater or a relay for each modulated carrier wave.
(1) Note. The subject matter of this subclass is limited to plural single channel repeaters; whenever plural independent messages are simultaneously transmitted, classification is elsewhere.

SEE OR SEARCH CLASS:

370Multiplex Communications,   for plural independent messages are simultaneously transmitted,
  
[List of Patents for class 455 subclass 13.2]    13.2Synchronizing of satellites or system:
 This subclass is indented under subclass 12.1.  Subject matter wherein stations in a system are regulated such that each transmits a carrier wave of the same frequency and phase as those carriers transmitted by the other stations.

SEE OR SEARCH CLASS:

370Multiplex Communications,   subclass 324 for time division multiple access synchronization of space satellites.
375Pulse or Digital Communications,   subclasses 354+ for digital network synchronization.
  
[List of Patents for class 455 subclass 13.3]    13.3With antennas feed network or multiple antennas switching:
 This subclass is indented under subclass 12.1.  Subject matter wherein the space satellite has more than one antenna or has a regulation means to control the selection of an antenna.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclasses 705+ for antennas with aircraft.
  
[List of Patents for class 455 subclass 13.4]    13.4Power control:
 This subclass is indented under subclass 12.1.  Subject matter including means to regulate the output power in the satellite system.
  
[List of Patents for class 455 subclass 14]    14With transmission line:
 This subclass is indented under subclass 7.  Subject matter where the repeater or relay is inserted in a waveguide or other type of transmission line.
  
[List of Patents for class 455 subclass 15]    15Two separate way transmission:
 This subclass is indented under subclass 7.  Subject matter where the relay or repeater operates in at least two directions.

SEE OR SEARCH CLASS:

178Telegraphy,   subclasses 71.1+ for automatic two-way repeaters specific to telegraphy.
370Multiplex Communications,   subclasses 276+ for duplex communications.
  
[List of Patents for class 455 subclass 16]    16Simultaneous using plural repeaters at each location:
 This subclass is indented under subclass 15.  Subject matter where the repeater operates in at least two directions at the same time by means of a plurality of repeaters at the same location.
  
[List of Patents for class 455 subclass 17]    17Plural modulated carriers:
 This subclass is indented under subclass 7.  Subject matter wherein there is more than one modulated carrier wave being repeated or relayed at the same time.

SEE OR SEARCH CLASS:

370Multiplex Communications,   subclasses 204+ for plural diverse modulation techniques.
  
[List of Patents for class 455 subclass 18]    18With delay or recording:
 This subclass is indented under subclass 7.  Subject matter including a device to time delay or make a permanent record of the modulated carrier wave.

SEE OR SEARCH CLASS:

327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 261+ for miscellaneous output waveform production delay.
333Wave Transmission Lines and Networks,   subclasses 138 through 164for passive delay networks.
  
[List of Patents for class 455 subclass 19]    19Common antenna:
 This subclass is indented under subclass 7.  Subject matter where the modulated carrier wave is received and transmitted on the same antenna.
  
[List of Patents for class 455 subclass 20]    20With frequency conversion:
 This subclass is indented under subclass 7.  Subject matter including apparatus to change the frequency of the modulated carrier wave.
(1) Note. For classification in this subclass it is not necessary that the carrier frequency of the transmitted signal be different from the carrier frequency of the received signal. For example, the frequency of the received carrier wave may be converted to a lower frequency for purposes of amplification and then be reconverted to the original frequency for transmission.

SEE OR SEARCH CLASS:

327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency control or conversion.
331Oscillators,   subclasses 37+ for means to produce a beat frequency by combining the output of two or more oscillators.
332Modulators,   appropriate subclasses for frequency conversion modulation systems, per se.
  
[List of Patents for class 455 subclass 21]    21With demodulator:
 This subclass is indented under subclass 20.  Subject matter including apparatus for removing the intelligence from the received signal.

SEE OR SEARCH CLASS:

329Demodulators,   for demodulators, per se.
330Amplifiers,   subclass 10 for direct current or low frequency alternating current amplifiers of the modulator-demodulator type.
  
[List of Patents for class 455 subclass 22]    22Plural conversion stages:
 This subclass is indented under subclass 20.  Subject matter including more than one successive conversion stage.

SEE OR SEARCH CLASS:

332Modulators,   especially subclasses 108, 119+, 145, and 151+ for plural modulation stage modulators.
  
[List of Patents for class 455 subclass 23]    23Frequency or phase modulation:
 This subclass is indented under subclass 7.  Subject matter where the carrier wave is modulated by varying its frequency or phase in accordance with the information signal.

SEE OR SEARCH CLASS:

329Demodulators,   subclasses 315+ for frequency demodulators and subclasses 345+ for phase demodulators.
332Modulators,   subclasses 183+ for modulation converters (e.g., FM. to A.M.); and subclasses 144+ and 117+ for phase or frequency modulators, per se.
  
[List of Patents for class 455 subclass 24]    24Transmitter-receiver feedback compensation:
 This subclass is indented under subclass 7.  Subject matter including apparatus to prevent unwanted feedback between the transmitter and the receiver.

SEE OR SEARCH THIS CLASS, SUBCLASS:

78,for a transceiver with transmitter-receiver interaction prevention.

SEE OR SEARCH CLASS:

327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 593 for miscellaneous oscillation prevention.
330Amplifiers,   subclasses 75+ for amplifiers with feedback means including negative feedback for preventing oscillation.
370Multiplex Communications,   subclasses 278 and 282+ for transmit/receive interaction control in duplex communications.
  
[List of Patents for class 455 subclass 25]    25Directive antenna:
 This subclass is indented under subclass 7.  Subject matter including an antenna which is more responsive in one direction than in another.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclass 18 for structure for reflecting radio waves; subclasses 100+ for means for sending and/or receiving radio wave energy which is characterized by some quality that varies according to the relative direction, position and/or plane or polarization of the sender and receiver; and subclasses 700+ for antennas, per se, including directional antennas and antennas combined with reflecting and/or refracting means.
  
[List of Patents for class 455 subclass 26.1]    26.1USE OR ACCESS BLOCKING (E.G., LOCKING SWITCH):
 This subclass is indented under the class definition.  Subject matter which blocks access to a signal source or otherwise limits usage of modulated carrier equipment.

SEE OR SEARCH CLASS:

194Check-Actuated Control Mechanisms,   appropriate subclasses for a coin controlled device of general utility.
380Cryptography,   appropriate subclasses for signal scrambling and subclasses 252 through 254for encryption by signal masking.
  
[List of Patents for class 455 subclass 39]    39TRANSMITTER AND RECEIVER AT SEPARATE STATIONS:
 This subclass is indented under the class definition.  Subject matter including at least one transmitting device which converts analog information signals (e.g., audio) into modulated carrier wave signals, a carrier wave transmission medium, and at least one receiving device whereby the information or modulating signal transmitted will be derived from the received modulated carrier wave signals.
(1) Note. A system, in order to be classified in this subclass and its indents must include a means whereby the information transmitted is transmitted by means of a sinusoidal electromagnetic carrier wave. Systems wherein the intelligence to be conveyed is transmitted by dot and dash (i.e., presence or absence of a unidirectional or direct current wave) are found elsewhere. Systems wherein the intelligence conveyed is pulse or digital information are found elsewhere. Systems wherein the intelligence to be conveyed by a varying current without a carrier wave are found elsewhere. Systems which are properly classifiable, as a result of some significantly claimed art limitations, in another class will not be classified here.
(2) Note. The subject matter classifiable here will generally comprise both the means for origination and modulating a carrier wave according to the information, desired to be transmitted, and a means for receiving the modulated carrier wave and deriving the desired information. However, where the claimed subject matter includes claims reciting the specific details of a transmitter or receiver or transceiver and broadly include another receiver, transceiver, or transmitter of different type by name only, the patent will be classified here and cross-reference down to the appropriate subclass below which contains the particular transmitter, transceiver, or receiver claimed.
(3) Note. The systems in this and the indented subclasses comprises at least one transmitter and receiver device which devices are located at an appreciable distance one from the other. However, patents in which the claimed subject matter includes transmitter-receiver means at a single station (transceiver) are also to be found here providing sufficient structure is recited whereby the transmitter-receiver means cooperates with and influence or is influenced by a further receiver or transmitter at a distance; providing, that the claimed subject matter does not include a structure limiting the system to use of radiant energy as defined in the definition of Class 343 or to use in some other art class device.

SEE OR SEARCH THIS CLASS, SUBCLASS:

7+,for transmitter-receiver repeater systems.
73+,for complete stations wherein the transmitter and receiver are at the same point.
91+,for transmitter, per se.
130+,for receivers, per se.
600+,for light wave communications.

SEE OR SEARCH CLASS:

178Telegraphy,   subclasses 2+ for various telegraph systems which are limited to the transmission and reception of telegraph signals; subclasses 24+ for teleprinting systems; subclasses 45+ for loaded carrier wave transmission lines; and subclass 118 for miscellaneous telegraph receivers.
244Aeronautics,   particularly subclasses 175+ for systems for automatically controlling aircraft by means of electrical apparatus which may utilize modulated carrier waves for control.
246Railway Switches and Signals,   particularly subclasses 7+ and 28+ for carrier wave systems employed in railway signalling.
307Electrical Transmission or Interconnection Systems,   subclass 117 for switching systems controlled by radiant energy; and subclass 129 for frequency responsive switching space discharge device or lamp systems.
315Electric Lamp and Discharge Devices: Systems,   subclasses 149+ for radiant energy controlled space discharge device or lamp systems.
318Electricity: Motive Power Systems,   subclass 16 for electric motor systems where the motor is controlled or supplied by space transmitted electromagnetic or electrostatic energy (including radio energy).
324Electricity: Measuring and Testing,   appropriate subclasses for systems for measuring or utilizing carrier waves.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   appropriate subclasses for miscellaneous circuits which may constitute elements of a system such as those classifiable in this class.
333Wave Transmission Lines and Networks,   appropriate subclasses for passive carrier wave transmission lines which may include passive network elements, attenuators or resonators which may have utility in the carrier wave systems of this class.
340Communications: Electrical,   appropriate subclasses for electrical signaling systems, especially subclasses 13.2-13.36 for selective signaling systems utilizing carrier waves; subclasses 286.01 through 286.14for miscellaneous signaling systems consisting of transmitters and receivers; subclasses 539.1-539.32 for systems automatically responsive to a condition and wherein the signal is transmitted via radio levels; and subclasses 870.01-870.44 for telemetering systems.
341Coded Data Generation or Conversion,   appropriate subclasses for code converters and subclasses 173 through 192for code generator or transmitter.
346Recorders,   subclass 37 for systems wherein a recorder is operated in response to the tuning of a radio receiver or receivers, e.g., community radio listening survey.
369Dynamic Information Storage or Retrieval,   subclasses 6+ for combined radio and phonograph systems.
370Multiplex Communications,   for analog carrier wave communication systems which have multiplexing.
375Pulse or Digital Communications,   for systems conveying or digital pulse information which may use modulated carrier waves.
380Cryptography,   for cryptographic communications.
411Expanded, Threaded, Driven, Headed, Tool-Deformed, or Lock-Threaded Fastener,   subclasses 50+ for code converters wherein a transmitter may receive its information in the form of a first code and transmit the information in the form of a dissimilar code; and subclasses 20+ and 173+ for code transmitters.
  
[List of Patents for class 455 subclass 40]    40Earth or water medium:
 This subclass is indented under subclass 39.  Subject matter where the ground (or water) supplies the natural medium for the transmission of the modulated carrier wave between the transmitter and receiver.
(1) Note. The subject matter of this subclass has a specific under ground (or underwater) structure at each station.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclass 719 for antenna systems buried underground or submerged underwater.
375Pulse or Digital Communications,   subclass 218 for pulse communication via an earth or water medium.
  
[List of Patents for class 455 subclass 41.1]    41.1Near field (i.e., inductive or capacitive coupling):
 This subclass is indented under subclass 39.  Subject matter including a limited range system where signal transfer from the transmitter to the receiver is inductive or capacitive.

SEE OR SEARCH THIS CLASS, SUBCLASS:

40,for underwater systems that may be inductive or capacitive.
41.2,for short range RF communication.

SEE OR SEARCH CLASS:

178Telegraphy,   subclass 43 for inductive telegraphy.
375Pulse or Digital Communications,   subclass 256 for near field pulse or digital communication.
  
[List of Patents for class 455 subclass 41.2]    41.2Short range RF communication:
 This subclass is indented under subclass 39.  Subject matter wherein communication between transmitter and receiver is directly implemented via radio frequency signal transmission over a short, limited distance.

SEE OR SEARCH THIS CLASS, SUBCLASS:

41.1,for near field inductive or capacitive coupling.
  
[List of Patents for class 455 subclass 41.3]    41.3To output device:
 This subclass is indented under subclass 41.2.  Subject matter including signal transfer from the transmitter to a remote output device.
(1) Note. Remote output devices may be audio speakers, printers, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:

66.1,for separate transmitter and receiver with diverse art device.
  
[List of Patents for class 455 subclass 42]    42Frequency or phase modulation:
 This subclass is indented under subclass 39.  Subject matter in which the intelligence or information to be transmitted is applied to a sine wave carrier in such a manner that the instantaneous frequency and/or phase angle of the sine wave carrier is caused to depart from a reference value by an amount proportional to the instantaneous amplitude of the modulating (intelligence) signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:

23,for frequency or phase modulated repeater.
29,for secret systems with carrier wobbling.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 207+ for telemetering systems utilizing frequency or phase modulation.
343Communications: Radio Wave Antennas,   subclass 14 for reflected wave systems utilizing pulse waves frequency or phase modulated; subclass 17.5 for reflected wave systems in general utilizing frequency or phase modulation; and subclasses 100+ for directive systems restricted to radio wave energy and utilizing frequency modulation.
359Optical: Systems and Elements,   various subclasses for optical communication.
375Pulse or Digital Communications,   subclasses 130 through 153for spread spectrum; and subclasses 223, 271, 302+, 329+, and 334+ for pulse communication by frequency or phase modulation of a carrier wave.
380Cryptography,   particularly subclass 322 for carrier wobbling by cryptographic equipment.
  
[List of Patents for class 455 subclass 43]    43With modification of frequencies of analog signal passed (e.g., pre-emphasis or de-emphasis):
 This subclass is indented under subclass 42.  Subject matter where the information or modulating signal is predistorted and/or preamplified prior to its modulation of the carrier wave.

SEE OR SEARCH CLASS:

332Modulators,   subclasses 123+ for frequency modulators, per se, with distortion introduction or control, e.g., pre-emphasis networks.
333Wave Transmission Lines and Networks,   subclasses 28+ for passive equalizing networks, per se.
  
[List of Patents for class 455 subclass 44]    44With stated modulation index:
 This subclass is indented under subclass 42.  Subject matter in which the effective frequency excursion or deviation is specified.
  
[List of Patents for class 455 subclass 45]    45Via subcarrier:
 This subclass is indented under subclass 42.  Subject matter where an intermediate frequency wave is modulated by a modulating signal representative of an intelligence or message and in turn is applied as a modulation signal to a main carrier wave, either alone or in conjunction with other subcarriers.
(1) Note. The frequency of the subcarrier is usually low relative to that of the main carrier.
  
[List of Patents for class 455 subclass 46]    46Suppressed carrier wave system:
 This subclass is indented under subclass 39.  Subject matter where the carrier component of a modulated wave is suppressed at the transmitter so that only the information bearing sideband or sidebands are transmitted and received.
(1) Note. Double or single sideband, suppressed carrier systems are found here.

SEE OR SEARCH THIS CLASS, SUBCLASS:

109,for suppressed carrier transmitter.
202,for suppressed carrier receivers.

SEE OR SEARCH CLASS:

332Modulators,   subclasses 167+ for a suppressed carrier double sideband type amplitude modulator, per se.
  
[List of Patents for class 455 subclass 47]    47Single or vestigial sideband system:
 This subclass is indented under subclass 39.  Subject matter where one sideband of the transmitted signal is largely or entirely suppressed while the second sideband has little or no suppression.
(1) Note. The carrier is not suppressed.
(2) Note. In this class, the term asymmetric sideband is generic to single and vestigial sideband.

SEE OR SEARCH THIS CLASS, SUBCLASS:

46,for systems where the carrier is suppressed.
109,for amplitude modulated transmitters.
203,for single sideband receivers.
204,for vestigial sideband receivers.

SEE OR SEARCH CLASS:

332Modulators,   subclasses 170+ for a single or vestigial sideband type amplitude modulator, per se.
348Television,   for vestigial sideband systems particular to television.
375Pulse or Digital Communications,   subclass 270 for similar systems for transmitting pulse data.
  
[List of Patents for class 455 subclass 48]    48Inverted sideband:
 This subclass is indented under subclass 39.  Subject matter where one of the sidebands is shifted by 180 degrees with respect to its normal phase relationship with respect to the other sideband.
  
[List of Patents for class 455 subclass 59]    59Single message via plural carrier wave transmission:
 This subclass is indented under subclass 39.  Subject matter where a single message or intelligence is transmitted by means of a plurality of carrier waves.
(1) Note. The subject matter to be found here will include systems in which the whole intelligence signal is divided into component parts, each of the components being modulated upon a separate carrier wave or systems in which the whole undivided intelligence signal is separately modulated upon separate carrier waves.

SEE OR SEARCH THIS CLASS, SUBCLASS:

13.1+,and 17, for repeaters utilizing plural channels.
27,for secret systems using a plurality of carrier waves.
42,for plural channel angle modulation systems.

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178Telegraphy,   subclass 32 for secret telegraph systems which may employ a plurality of carrier waves or alternating current waves.
375Pulse or Digital Communications,   subclasses 260+ for pulse modulated carrier wave systems using plural channels to transmit a single pulse train.
380Cryptography,   particularly subclass 34 for a cryptographic system utilizing plural carrier frequencies.
  
[List of Patents for class 455 subclass 60]    60Different phases of same frequency carrier:
 This subclass is indented under subclass 59.  Subject matter in which the message is modulated onto different phases (e.g., different polarizations) of a carrier wave and each phase is then separately transmitted.
  
[List of Patents for class 455 subclass 61]    61Single message via plural modulation of single carrier:
 This subclass is indented under subclass 39.  Subject matter including modulation of a single carrier wave by a plurality of separate and distinct modulation signals each representing a portion of the intelligence to be transmitted.

SEE OR SEARCH THIS CLASS, SUBCLASS:

22,for repeaters with plural conversion stages.
28,for plural modulation of a single carrier wave for secrecy.

SEE OR SEARCH CLASS:

375Pulse or Digital Communications,   subclass 269 for pulse modulated carrier wave systems with plural modulation of a single carrier.
380Cryptography,   particularly subclasses 31+ for a cryptographic system utilizing plural modulation of a single carrier wave.
  
[List of Patents for class 455 subclass 62]    62Optimum frequency selection:
 This subclass is indented under subclass 39.  Subject matter in which a frequency of operation is selected with is optimum with respect to a given criteria.
  
[List of Patents for class 455 subclass 63.1]    63.1Distortion, noise, or other interference prevention, reduction, or compensation:
 This subclass is indented under subclass 39.  Subject matter with provision for reduction, compensation or elimination of an unwanted signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:

8,for failure compensation in a repeater.
10,for fading compensation in repeaters.
78through 83, for transceivers with transmitter receiver interaction prevention.
119,for transmitters with carrier frequency stabilization.
134,and 135, for plural receivers with output selecting according to signal strength or quality.
222through 224, for noise controlled squelch in a receiver.
234.1through 253.2, for automatic gain or volume control in a receiver.
255through 265, for local oscillator frequency control in a receiver.
267,for tone control in a receiver.
268,for fidelity control in a receiver.
278.1through 279.1, for receiver plural wave collector noise or interference elimination.
283through 288, for receiver wave collector interference or noise elimination.
296through 312, for receiver noise or interference elimination.
501through 506, for similar subject matter in plural transmitter/receiver systems.
701through 703, for tone coded squelch.
  
[List of Patents for class 455 subclass 63.2]    63.2System with hierarchical coverage areas:
 This subclass is indented under subclass 63.1.  Subject matter including interference prevention, reduction, or compensation in an hierarchical communication system which has multiple structural communication levels (e.g.,overlaid coverage areas, smaller coverage areas overlapped by larger coverage areas).

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450,and 509, for channel allocation.
  
[List of Patents for class 455 subclass 63.3]    63.3Frequency switching:
 This subclass is indented under subclass 63.1.  Subject matter including selecting between frequencies or channels to prevent interference.
  
[List of Patents for class 455 subclass 63.4]    63.4Directional antenna:
 This subclass is indented under subclass 63.1.  Subject matter in which a focus beam is provided in a desired direction of transmission or reception.

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25,for an antenna which is more responsive in one direction than another in a repeater system.

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342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, and Radio Navigation),   subclasses 359 and 367 for directive system antenna orientation or a directive communication system in general, respectively.
  
[List of Patents for class 455 subclass 64]    64Plasma source or barrier:
 This subclass is indented under subclass 63.1.  Subject matter where the distortion and noise is caused by a plasma (e.g., space craft re-entry).
  
[List of Patents for class 455 subclass 65]    65Anti-multipath:
 This subclass is indented under subclass 63.1.  Subject matter where there is prevention, reduction, or compensation for distortion caused by the modulated carrier wave traveling from the transmitter to the receiver by plural paths of differing lengths.

SEE OR SEARCH THIS CLASS, SUBCLASS:

10,for fading compensation in a repeater.
504+,for fading compensation in a plural transmitter or receiver systems.
  
[List of Patents for class 455 subclass 66.1]    66.1Having diverse art device:
 This subclass is indented under subclass 39.  Subject matter including a separated transmitter and receiver system along with another art device or structure having an added purpose or independent utility other than to perfect an element of the system and in which the utility of the other art device or structure is not destroyed or disturbed by its removal from the system.
(1) Note. Combination with specific art having subclass provided for in other class is classified in the other class. See search class note below.

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40Card, Picture, or Sign Exhibiting,   subclasses 455 through 457for changeable exhibitors with sound in which the source of the sound may be a radio receiver.
102Ammunition and Explosive,   subclass 214 for fuses utilizing a radio wave.
116Signals and Indicators,   subclasses 241 through 263for position indicators for radio apparatus.
178Telegraphy,   subclasses 118 through 120for telegraph receivers which may be combined with other art devices.
194Check-Actuated Control Mechanisms,   appropriate subclasses for a check controlled radio apparatus combined with other art device.
248Supports,   subclass 27.1 for means for supporting an instrument in a panel.
307Electrical Transmission or Interconnection Systems,   subclasses 9.1 through 10.8for vehicle mounted systems in which the vehicle may provide power means for a radio telephone or other receiver means and subclasses 154-157 for miscellaneous systems with particular load device or load device combination.
312Supports: Cabinet Structure,   subclass 7.1 for radio type cabinets.
340Communications: Electrical,   subclass 539 for a condition responsive indicating system with a radio coupling link.
343Communications: Radio Wave Antennas,   subclass 6 for reflected wave (e.g., radar) systems combined with diverse type radiant energy systems.
346Recorders,   subclass 25 for recorders combined with other nonrecording devices; and subclass 37 for recorders combined with a radio receiver and tuning responsive and for the purpose of determining the listening habits of the users of a receiver.
362Illumination,   appropriate subclasses for combined light and other art device structure.
368Horology: Time Measuring Systems or Devices,   subclasses 10 through 14for clocks combined with other devices where the claimed combination does not include characteristics of the device not necessary to the function of the horological device.
369Dynamic Information Storage or Retrieval,   subclasses 6 through 12for combined radio and phonograph systems.
386Motion Video Signal Processing for Recording or Reproducing,   appropriate subclasses for television or video recording and reproduction.
396Photography,   subclass 434 for a camera combined with a radio.
446Amusement Devices: Toys,   subclasses 297 through 303for a figure toy having a sounder, wherein the figure may act as a receptacle for a receiver.
  
[List of Patents for class 455 subclass 67.7]    67.7With indication (e.g., visual or voice signalling, etc.):
 This subclass is indented under subclass 67.1.  Subject matter having means for making a condition pertaining to the testing or measuring of the system perceptible to a human operator.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 539.1 through 539.32for generic condition indicating system over radio link.
  
[List of Patents for class 455 subclass 67.11]    67.11Having measuring, testing, or monitoring of system or part:
 This subclass is indented under subclass 39.  Subject matter which relates to means intended solely for the purpose of and adapted to (a) adjust the frequency setting of a carrier wave generation means or determine the output frequency or some other characteristics of a transmitter means; (b) adjust the frequency setting of a local oscillator, a tuning means or other stages of a receiver means in accordance with a standard frequency; c) compare the frequency of a resonant input or output circuit of a receiver or transmitter with a standard frequency for the purpose of setting a tuning position indicator or dial to correspond to maximum transmitter or receiver output at the standard frequency; and (d) determine the operating characteristics of the whole or selected components of the system under prescribed conditions of operation.
  
[List of Patents for class 455 subclass 67.12]    67.12Using a chamber (e.g., room testing or audio surveillance, etc.):
 This subclass is indented under subclass 67.11.  Subject matter wherein the measuring, testing, or monitoring is conducted in a confined housing or in a relatively close location.
(1) Note. For example, method or device for locating an inter-modular or interference source in a close proximity to a desired transmitting source, or detecting the presence of a hidden transmitter, e.g., eavesdropping device.
  
[List of Patents for class 455 subclass 67.13]    67.13Noise, distortion, or unwanted signal detection (e.g. quality control etc.):
 This subclass is indented under subclass 67.11.  Subject matter having means to detect any undesired electrical disturbance within the useful frequency band arising from sources internal or external to the system (e.g., cross-talk, power induction, atmospheric noise, etc.), or any undesired self-sustained oscillation existing in the system, or other unwanted signals tending to interfere with the operation of the system.
  
[List of Patents for class 455 subclass 67.14]    67.14Using a test signal:
 This subclass is indented under subclass 67.11.  Subject matter wherein a signal of predetermined frequency (i.e., reference signal) is sent over the system for testing or measuring purposes (e.g., emulation, loop-back, etc.).
  
[List of Patents for class 455 subclass 67.15]    67.15Of a microwave link or system:
 This subclass is indented under subclass 67.11.  Subject matter involves system using communication signals in the range of microwave frequencies (i.e., approximately 1000 MHZ and above).
  
[List of Patents for class 455 subclass 67.16]    67.16Phase measuring (e.g., group delay, propagation effect, etc.):
 This subclass is indented under subclass 67.11.  Subject matter including means to measure the change in phase of propagating waves.
(1) Note. Phase measurement may be used for developing a suitable control for equalization, attenuation compensation, synchronization, etc.
  
[List of Patents for class 455 subclass 68]    68With control signal:
 This subclass is indented under subclass 39.  Subject matter wherein the communication apparatus includes an intelligence signal transmitted from a transmitter to a receiver over distances large compared with their dimensions and where one of either the transmitter or receiver includes controlling means which causes some modification of the operation of the other.
  
[List of Patents for class 455 subclass 69]    69Transmitter controlled by signal feedback from receiver:
 This subclass is indented under subclass 68.  Subject matter wherein the controlling means is located at the receiver and modifies the operation of the transmitter in response thereto.
  
[List of Patents for class 455 subclass 70]    70Receiver control signal originates at message transmitter:
 This subclass is indented under subclass 68.  Subject matter wherein the controlling means is located at the transmitter and modifies the operation of the receiver in response to said controlling means.
(1) Note. The controlling means may send a reference or controlling modulation component on the carrier wave. However, such component must be distinct from the message, as receivers responsive to the inherent characteristics of the message signal are excluded from this subclass.
  
[List of Patents for class 455 subclass 71]    71Frequency control:
 This subclass is indented under subclass 70.  Subject matter where the frequency to which the receiver is tuned is controlled.

SEE OR SEARCH THIS CLASS, SUBCLASS:

151.1,for remote control of channel or station selection in a receiver.
  
[List of Patents for class 455 subclass 72]    72For compression and expansion of message signal (i.e., companding):
 This subclass is indented under subclass 70.  Subject matter wherein the range of variation of the modulating parameter is decreased at the transmitter and expanded in the complementary manner in the receiver.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   subclass 14 for companding systems, per se.
  
[List of Patents for class 455 subclass 73]    73TRANSMITTER AND RECEIVER AT SAME STATION (E.G., TRANSCEIVER):
 This subclass is indented under the class definition.  Subject matter having both a signal transmitter and a signal receiver at a common geographic location for transmission and reception of separate signals.
(1) Note. The transmitter and receiver at a common location are hereafter termed "a station" in these definitions.
(2) Note. The simultaneous separation of a transmitter and receiver is a duplex operation and is classified in Class 370, Multiplex Communications, subclasses 276+.

SEE OR SEARCH THIS CLASS, SUBCLASS:

1,for an interference signal transmitter, which may include a receiver at the same station.
606+,for a complete light wave communication station.

SEE OR SEARCH CLASS:

370Multiplex Communications,   subclasses 276+ for duplex systems, see (2) Note above.
375Pulse or Digital Communications,   subclass 219 for similar devices which handle pulse and digital signals.
  
[List of Patents for class 455 subclass 74]    74Convertible (e.g., to diverse art device):
 This subclass is indented under subclass 73.  Subject matter wherein at least a portion of the transceiver circuitry is alternatively operable as a portion of another electrical sound signal processing system.
(1) Note. The term convertible is intended to include a receiver for a different frequency band (e.g., broadcast receiver).
  
[List of Patents for class 455 subclass 74.1]    74.1Cordless/corded conversion:
 This subclass is indented under subclass 74.  Subject matter wherein the transceiver includes a structure for transforming a wired transmission capability to a wireless transmission capacity or vice versa.
  
[List of Patents for class 455 subclass 75]    75With frequency stabilization (e.g., automatic frequency control):
 This subclass is indented under subclass 73.  Subject matter having means to prevent or compensate for variation in the operating frequency of the transceiver.

SEE OR SEARCH THIS CLASS, SUBCLASS:

113,and 119, for transmitter with automatic frequency control or stabilization.
164.1,173.1, 192.1+, and 257, for receivers with automatic frequency control or stabilization.

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331Oscillators,   subclasses 1+ for oscillators with automatic frequency control.
  
[List of Patents for class 455 subclass 76]    76Synthesizer:
 This subclass is indented under subclass 75.  Subject matter in which a single stable oscillator is used as a source of one or more frequencies derived therefrom by frequency multiplication or division.
(1) Note. The stable oscillator is often crystal controlled or phase-locked.

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165.1,and 183.1+, for receivers with synthesizers.

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331Oscillators,   subclass 1 for synthesizers in general.
  
[List of Patents for class 455 subclass 77]    77With tuning:
 This subclass is indented under subclass 73.  Subject matter having means to control or adjust the frequency of the transmitted or received signal; or the loading or adjustment of the radio frequency circuits is varied.

SEE OR SEARCH THIS CLASS, SUBCLASS:

120+,for transmitter tuning.
150.1,for receiver tuning.

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334Tuners,   for passive tuning circuits in general.
  
[List of Patents for class 455 subclass 78]    78With transmitter-receiver switching or interaction prevention:
 This subclass is indented under subclass 73.  Subject matter wherein the transmitter and receiver are made orthogonal by alternatively actuating the transmitter or receiver or by isolation circuitry.

SEE OR SEARCH CLASS:

370Multiplex Communications,   subclasses 278 and 282+ for transmit/receive interaction control in duplex communications.
  
[List of Patents for class 455 subclass 79]    79Automatic (e.g., voice-operated):
 This subclass is indented under subclass 78.  Subject matter wherein the switching device is other than manually operated.
(1) Note. Such means includes voice operated switching.

SEE OR SEARCH THIS CLASS, SUBCLASS:

116,for transmitters automatically actuated in response to voice, etc.
  
[List of Patents for class 455 subclass 80]    80With distributed parameter coupling:
 This subclass is indented under subclass 79.  Subject matter having a distributed parameter transmitter line coupling the transmitter and receiver portions of the transceiver to an antenna.

SEE OR SEARCH CLASS:

333Wave Transmission Lines and Networks,   subclasses 100+ for branched circuits.
  
[List of Patents for class 455 subclass 81]    81Waveguide:
 This subclass is indented under subclass 80.  Subject matter wherein the transmission line is a hollow conductor.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 593 for miscellaneous circuits with a distributed parameter element (e.g., waveguide).
333Wave Transmission Lines and Networks,   subclass 13 for waveguides having gas breakdown switching (e.g., T-R) tubes; subclasses 100+ for branching networks; and subclass 13 for hybrid transmit-receiver isolators.
  
[List of Patents for class 455 subclass 82]    82Common antenna:
 This subclass is indented under subclass 79.  Subject matter where the transmitter and the receiver use the same antenna.
  
[List of Patents for class 455 subclass 83]    83Single antenna switched between transmitter and receiver:
 This subclass is indented under subclass 78.  Subject matter which has a single antenna which is alternately connected to the transmitter and receiver.

SEE OR SEARCH THIS CLASS, SUBCLASS:

82,for a single antenna automatically switched between transmitter and receiver.
  
[List of Patents for class 455 subclass 84]    84With a common signal processing stage:
 This subclass is indented under subclass 73.  Subject matter having an active element which performs a signal processing or generating function in the transmitter portion of the apparatus during signal transmission and in the receiver portion of the apparatus during signal reception.
(1) Note. The terms "active" and "signal processing" are used to exclude common use of nonprocessing elements, e.g., antennas and power supplies.
  
[List of Patents for class 455 subclass 85]    85Transmitter oscillator used as detector:
 This subclass is indented under subclass 84.  Subject matter wherein the active element circuitry which produces the carrier signal during transmission functions as a demodulator during signal reception.
(1) Note. The term demodulator used above excludes heterodyning mixers. Rather it includes only those devices producing a signal which is a replica of the original modulating information signal.
  
[List of Patents for class 455 subclass 86]    86Transmitter oscillator used as local oscillator:
 This subclass is indented under subclass 84.  Subject matter wherein the active element circuitry which produces the carrier during transmission also produces the oscillatory signal with which the received signal is heterodyned.
  
[List of Patents for class 455 subclass 87]    87Tunable or variable:
 This subclass is indented under subclass 86.  Subject matter where the frequency of the local oscillator is variable or changeable.
  
[List of Patents for class 455 subclass 88]    88Transceiver controlling a separate transceiver or receiver:
 This subclass is indented under subclass 73.  Subject matter wherein the transceiver is operative to produce a signal controlling the operation of another transceiver or a receiver at the same location.
(1) Note. The controlling signal may be either a signal produced for control purposes or may be the normal transmitted signal of the transceiver.
(2) Note. Such control may include, for example, switching from a stand-by condition.

SEE OR SEARCH THIS CLASS, SUBCLASS:

132+,for diversity-type receivers which may control one another.
352,for receivers which are remotely controlled.

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340Communications: Electrical,   subclasses 1.1 through 16.1for various remote control systems not limited to modulated carrier waves and selective paging systems.
  
[List of Patents for class 455 subclass 90.1]    90.1Having particular application (e.g., avalanche victim assistance) of a transceiver:
 This subclass is indented under subclass 73.  Subject matter wherein a transceiver other than a radiotelephone is designed for or utilized in a specific environment.
  
[List of Patents for class 455 subclass 90.2]    90.2Having particular configuration (e.g., C.B. or walkie-talkie) of a transceiver:
 This subclass is indented under subclass 73.  Subject matter wherein a transceiver other than a radiotelephone has a particular arrangement of its component parts.
(1) Note. This includes, for example, such configurations as citizen band (CB) radio, walkie-talkie, Smart Mobile Radio (SMR), or Push To Talk (PTT).
  
[List of Patents for class 455 subclass 90.3]    90.3Having particular housing or support of a transceiver:
 This subclass is indented under subclass 73.  Subject matter wherein a transceiver other than a radiotelephone has a specified enclosure or support means.

SEE OR SEARCH THIS CLASS, SUBCLASS:

347,for a receiver housing.

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248Supports,   subclasses 309.1 through 316.8for bracket means for holding a radio that does not claim radio structure.
312Supports: Cabinet Structure,   subclass 7.1 for radio cabinets, per se, that do not claim radio structure.
  
[List of Patents for class 455 subclass 91]    91TRANSMITTER:
 This subclass is indented under the class definition.  Subject matter comprising apparatus for generating and modulating a carrier wave and usually including the coupling of the modulated carrier wave to the transmission medium.

SEE OR SEARCH THIS CLASS, SUBCLASS:

1,for an interference signal transmitter.
7+,for a repeater or relay system having a transmitter stage.
26+,for a secret system transmitter.
39+,for systems having a transmitter and a receiver.
88+,for a transceiver.

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178Telegraphy,   subclasses 79+ for telephone transmitters.
219Electric Heating,   subclasses 600+ for inductive heating, subclasses 678+ for microwave heating, and subclasses 764+ for capacitive dielectric heating.
250Radiant Energy,   appropriate subclasses for radiant energy transmitters in general.
310Electrical Generator or Motor Structure,   appropriate subclasses for electrical generators.
315Electric Lamp and Discharge Devices: Systems,   subclass 34 for a particular electron discharge tube device in a circuit including an antenna.
322Electricity: Single Generator Systems,   appropriate subclasses for generating electricity.
331Oscillators,   appropriate subclasses.
332Modulators,   appropriate subclasses for modulators, per se.
340Communications: Electrical,   appropriate subclasses for traffic and vehicle communications; subclasses 1.1 through 16.1for selective (e.g., remote control, etc.), including subclasses 7.1-7.63 for selective paging transmitters; subclass 311.2 for nonselective paging transmitters; subclasses 539.1-539.32 for alarms with a radio link; subclasses 853.1-856.4 for well bore communications; and subclasses 870.18-870.24 for telemetering, all which may include modulated carrier waves.
343Communications: Radio Wave Antennas,   subclasses 5+ for reflected or returned wave systems; and subclasses 100+ for antennas which may nominally recite a transmitter.
348Television,   subclasses 469+ and 723+ for television transmitters.
375Pulse or Digital Communications,   particularly subclasses 295+ for similar transmission of pulse or digital signals.
380Cryptography,   appropriate subclasses for a cryptographic telecommunication system.
  
[List of Patents for class 455 subclass 92]    92Remote control of a transmitter:
 This subclass is indented under subclass 91.  Subject matter including structure for modifying or controlling the operation of the transmitter from a point removed some distance from the transmitter.
(1) Note. The controlling function may be performed automatically or manually.

SEE OR SEARCH THIS CLASS, SUBCLASS:

352,for remote control of a receiver.

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340Communications: Electrical,   subclasses 12.5 , 12.51, 13.25, and 13.26 for radio remote control in selective signaling systems.
  
[List of Patents for class 455 subclass 93]    93Convertible to different type (e.g., AM to FM):
 This subclass is indented under subclass 91.  Subject matter wherein the transmitter is constructed so that it may be changed from one type of transmitter to a different type of transmitter, such as, for example, changed from a crystal controlled to a tunable transmitter or change from FM to AM.
(1) Note. If one alternative is pulse, e.g., digital transmission, the system is classified in Class 375.

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375Pulse or Digital Communications,   subclass 216 for transmitters convertible to/from pulse modulated carrier wave.
  
[List of Patents for class 455 subclass 94]    94Alternator:
 This subclass is indented under subclass 91.  Subject matter where the transmitter power is generated by a dynamo-electric radio frequency device.

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178Telegraphy,   subclass 116 for spark gap or arc discharge transmitters.
  
[List of Patents for class 455 subclass 95]    95Mobile or portable:
 This subclass is indented under subclass 91.  Subject matter constructed to be transportable by vehicle or person.
(1) Note. The transmitters in this and the indented subclasses may be installed upon a vehicle and operated while the vehicle is in motion or may be installed or positioned on the vehicle to be ejected therefrom as in the subclass below.
(2) Note. Transmitters, per se, which send signals which indicate relative direction or position are classified elsewhere.

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11.1,for mobile or portable repeaters.
90.1through 90.3, 517, 569.2, and 575.1-575.9, for mobile or portable transceiver.
96,for transmitter ejected from a mobile vehicle.
517+,and 575, for mobile or portable systems.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 22+ for vehicle or traffic environment signalling; and subclasses 500+ for condition responsive indicating systems.
343Communications: Radio Wave Antennas,   subclasses 100+ for directive type transmitters or receivers or receivers, per se.
  
[List of Patents for class 455 subclass 96]    96Transmitter ejected from moving vehicle:
 This subclass is indented under subclass 95.  Subject matter where the transmitter is ejected from a mobile vehicle.
(1) Note. The transmitter may be automatically ejected (e.g., responsive to the impact of a crash) or manually ejected by operation of a switch.

SEE OR SEARCH CLASS:

244Aeronautics,   subclasses 138+ for safety lowering devices in general of the aeronautical type.
340Communications: Electrical,   subclasses 22+ for vehicle or traffic environment signalling.
343Communications: Radio Wave Antennas,   subclasses 100+ for sending of radio wave energy which is characterized by relative direction or position and is not ejected or activated by a moving vehicle.
  
[List of Patents for class 455 subclass 97]    97With antenna ejection or external support:
 This subclass is indented under subclass 95.  Subject matter including provision for ejecting or extending an antenna from the transmitter, or having provision for externally supporting an antenna (e.g., a balloon).
(1) Note. The antenna ejection or antenna support may or may not be automatically operated.
  
[List of Patents for class 455 subclass 98]    98With aircraft, satellite, or projectile:
 This subclass is indented under subclass 95.  Subject matter combined with or carried by an air or space vehicle.

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96,if the transmitter is ejected from the vehicle.
  
[List of Patents for class 455 subclass 99]    99With vehicle:
 This subclass is indented under subclass 95.  Subject matter carried by or combined with a vehicle such as surface craft, submarine, automobile, or other land or waterborne vehicle.

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98,for transmitters combined with aircraft.

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340Communications: Electrical,   subclasses 22+ for vehicle or traffic environment signalling.
343Communications: Radio Wave Antennas,   subclasses 709 and 710 for waterborne antennas.
441Buoys, Rafts, and Aquatic Devices,   subclass 89 for body attached buoyant devices combined with analog modulated carrier wave communications.
  
[List of Patents for class 455 subclass 100]    100Body attached or connected:
 This subclass is indented under subclass 95.  Subject matter which is shaped to fit the body or be supported by the body.
(1) Note. For classification in this subclass, a portion of the transmitter must be shaped to fit or be supported by the body such as an antenna or microphone attached to the body. Small hand carried transmitters with no portion thereof connected to the body are classified elsewhere in this class.

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95,for small hand carried transmitters with no portion thereof connected to the body.

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340Communications: Electrical,   subclasses 573.1+ for transmitters responsive to the condition of a human which may be attached or connected to the body.
343Communications: Radio Wave Antennas,   subclass 718 for body attached or supported antennas.
  
[List of Patents for class 455 subclass 101]    101Diversity:
 This subclass is indented under subclass 91.  Subject matter where two or more channels are transmitted via different paths, frequencies, or times of transmission.
(1) Note. Subject matter classified here is distinguished from multiplex, Class 370, in that no specialized receiver is needed for discerning the separate channels.
(2) Note. Subject matter classified here is limited to the transmission of a single message at a time over the channels.
(3) Note. Some system classified here are directed toward reducing fading at the receiver.
  
[List of Patents for class 455 subclass 102]    102Plural modulation:
 This subclass is indented under subclass 91.  Subject matter in which the carrier wave is modulated at least twice prior to transmission.
(1) Note. The plural modulation may be of the same or diverse types, and is usually sequential.

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332Modulators,   subclasses 119+ , 145 and 151+ for plural modulation, per se.
  
[List of Patents for class 455 subclass 103]    103Plural separate transmitters or channels:
 This subclass is indented under subclass 91.  Subject matter where there are plural transmission channels formed of separate complete transmitters, capable of independent operation.
(1) Note. The plural transmitters may be interconnected to a common antenna, by a common power supply or by a common control signal path.
(2) Note. Systems using multiplex techniques to combine separate messages and apply to a common antenna are classified in Class 370, subclasses 339+.
  
[List of Patents for class 455 subclass 104]    104Carrier and sidebands separately transmitted:
 This subclass is indented under subclass 103.  Subject matter where separate channels are provided for transmitting the carrier and the sideband components of a modulated carrier wave.
(1) Note. Also included in this subclass are transmitters having separate channels for the carrier and sideband components and with means to produce a rotating field pattern.
  
[List of Patents for class 455 subclass 105]    105Common frequency:
 This subclass is indented under subclass 103.  Subject matter where the plural transmitters broadcast on the same frequency.
(1) Note. Systems with frequency control of the second, spaced, or remote, transmitter are classified in subclass 92 above.
  
[List of Patents for class 455 subclass 106]    106Modulation by absorption, shielding, or reflecting:
 This subclass is indented under subclass 91.  Subject matter including structure spaced from or external to the antenna which modulates the carrier radiated from the antenna, such as by absorption, shielding, or reflecting.
(1) Note. The radiated carrier may be angle modulated or it may be amplitude modulated.

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121+,and 129+, for systems not limited to modulation systems.

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343Communications: Radio Wave Antennas,   subclasses 753+ for radio antennas with external radio wave refractor.
  
[List of Patents for class 455 subclass 107]    107With variation of antenna impedance or dimension for modulation:
 This subclass is indented under subclass 91.  Subject matter where the carrier wave is modulated, under control of the modulating intelligence signal, by varying the impedance or dimension of the antenna.

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121+,for systems in which the antenna circuit is varied for tuning.
129+,for systems in which the antenna coupling is explicitly shown and varied therefor.
269+,for systems of antenna combined with receiver for similar coupling arrangements, noting especially 289.
  
[List of Patents for class 455 subclass 108]    108Amplitude modulation:
 This subclass is indented under subclass 91.  Subject matter where the amplitude of the carrier is varied under control of the intelligence to be transmitted.
  
[List of Patents for class 455 subclass 109]    109Vestigial or single sideband or suppressed carrier:
 This subclass is indented under subclass 108.  Subject matter where less than two complete sidebands are transmitted, with or without the carrier or two complete sidebands are transmitted without the carrier.

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46,for suppressed carrier wave systems.
47,for single or vestigial sideband systems.

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332Modulators,   subclasses 167+ for a suppressed carrier double sideband type amplitude modulator.
348Television,   subclasses 723+ for vestigial sideband television transmitters.
  
[List of Patents for class 455 subclass 110]    110Angle modulation:
 This subclass is indented under subclass 91.  Subject matter where the frequency or phase of the carrier wave is varied or modulated under control of the intelligence that is transmitted.
  
[List of Patents for class 455 subclass 111]    111Including distributed parameter structure:
 This subclass is indented under subclass 110.  Subject matter including, as a significant part of the transmitter, a structure with distributed parameter wave transmission means or circuits designed to simulate the impedance characteristics of distributed parameter wave transmission means.

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333Wave Transmission Lines and Networks,   appropriate subclasses for distributed electric parameter devices, per se.
  
[List of Patents for class 455 subclass 112]    112With frequency multiplication or division:
 This subclass is indented under subclass 110.  Subject matter where a signal at one frequency is converted to a second frequency which is a multiple or sub-multiple of the first frequency.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control.
363Electric Power Conversion Systems,   subclasses 157+ for power frequency conversion.
  
[List of Patents for class 455 subclass 113]    113With frequency control:
 This subclass is indented under subclass 110.  Subject matter where the operating frequency of the transmitter is controlled or regulated.
  
[List of Patents for class 455 subclass 114.1]    114.1Having harmonic radiation suppression:
 This subclass is indented under subclass 91.  Subject matter having provision for the reduction or suppression of a sinusoidal wave having a frequency which is an integral multiple of a fundamental frequency at an antenna.
  
[List of Patents for class 455 subclass 114.2]    114.2Noise or interference elimination:
 This subclass is indented under subclass 91.  Subject matter having structure to suppress the influence of extraneous electric fields upon transmitter circuitry.
  
[List of Patents for class 455 subclass 114.3]    114.3Predistortion (e.g., for power amplifier):
 This subclass is indented under subclass 114.2.  Subject matter where a transmitted signal may prior to transmission, be distorted in a manner complementary to the distortion introduced in the power amplifier, antenna or transmission medium, etc.

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375Pulse or Digital Communications,   subclasses 296 through 297for predistortion techniques in the transmission of pulse or digital signals.
  
[List of Patents for class 455 subclass 115.1]    115.1Measuring, testing, or monitoring of transmitter:
 This subclass is indented under subclass 91.  Subject matter having measuring, testing, or monitoring of the signals transmitted.
(1) Note. The transmitter must be claimed in detail along with the monitoring means, claimed broadly or in detail.

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324Electricity: Measuring and Testing,   subclasses 76.11 through 157for measuring sensing or testing electricity, per se.
340Communications: Electrical,   subclass 653 for condition of electronic circuit or component responsive indication.
  
[List of Patents for class 455 subclass 115.2]    115.2Using a test signal:
 This subclass is indented under subclass 115.1.  Subject matter wherein a signal of predetermined frequency (i.e., reference signal) is involved in the process of testing or measuring.
  
[List of Patents for class 455 subclass 115.3]    115.3Signal strength:
 This subclass is indented under subclass 115.1.  Subject matter including a means for measuring a signal intensity level.
  
[List of Patents for class 455 subclass 115.4]    115.4Having meter or indicator:
 This subclass is indented under subclass 115.1.  Subject matter including a means for displaying to a human observer information concerning a transmitter characteristic being measured.
  
[List of Patents for class 455 subclass 116]    116Carrier amplitude control (e.g., voice operated on/off):
 This subclass is indented under subclass 91.  Subject matter where the amplitude of the carrier signal is controlled responsive to the modulation signal.
(1) Note. For classification in this subclass the amplitude of the carrier is varied responsive to the modulation signal, for example, the carrier amplitude is reduced or cut off when the modulating signal is absent or reduced.
  
[List of Patents for class 455 subclass 117]    117With electrical protection of transmitter circuit or operator:
 This subclass is indented under subclass 91.  Subject matter where the transmitter circuits or operators are protected from damage or injury such as from overload or malfunction of a component within the transmitter.
(1) Note. For classification in this subclass some detail of the transmitter must be claimed along with the protective means, claimed broadly or in detail, for protecting the operator or transmitter. Where the transmitter is claimed broadly (such as by name only) and the protective means is claimed in detail, classification is with the protective means.
(2) Note. The overload may be the result of a defective tube or other component within the transmitter or it may be the result of an external fault such as an antenna failure, lightning, or of transmission line arc-over.
(3) Note. Transmitters with temperature modifier or control means, such, for example, as cooling are in this subclass.
(4) Note. Transmitters with automatic condition responsive alarm are elsewhere in this class.
(5) Note. Operator protection is also included here.

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115.1through 115.4, for transmitters with automatic condition responsive alarm.

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307Electrical Transmission or Interconnection Systems,   subclasses 326+ for generic personnel safety means.
330Amplifiers,   subclass 51 for amplifiers with automatic disabling switch.
331Oscillators,   subclass 62 for oscillators with circuit means.
361Electricity: Electrical Systems and Devices,   subclasses 1+ for safety and protection of electrical systems and devices.
  
[List of Patents for class 455 subclass 118]    118Frequency conversion:
 This subclass is indented under subclass 91.  Subject matter where a signal is converted from a first frequency to a second frequency.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control.
331Oscillators,   subclasses 51 and 53 for plural oscillator frequency multipliers and dividers.
363Electric Power Conversion Systems,   subclasses 157+ for electric power frequency conversion.
  
[List of Patents for class 455 subclass 119]    119Carrier frequency stabilization:
 This subclass is indented under subclass 91.  Subject matter including provision to prevent or compensate for undesirable drift or change in the frequency at which the transmitter is operating.
(1) Note. The prevention or compensation for the drift or change in frequency of the transmitter may be automatically controlled.
  
[List of Patents for class 455 subclass 120]    120Including tuning:
 This subclass is indented under subclass 91.  Subject matter including a resonant network or crystal whose resonant frequency may be varied (tuned) to control or modify the operating frequency of the transmitter, or which may be substituted for other resonant networks or crystals, as by switching, to control or modify the operating frequency of the transmitter.
  
[List of Patents for class 455 subclass 121]    121In antenna circuit:
 This subclass is indented under subclass 120.  Subject matter wherein the tuning structure or circuitry is located within the antenna or forms part of the antenna coupling circuit.

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129,for a transmitter with an antenna circuit with variable coupling thereto.
  
[List of Patents for class 455 subclass 122]    122With saturable reactor:
 This subclass is indented under subclass 121.  Subject matter having a magnetic core reactor which is controlled by adjusting a superimposed unidirectional magnetic flux to effect adjustment of saturation of the core.

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307Electrical Transmission or Interconnection Systems,   subclasses 401+ for saturable reactor systems, in general.
  
[List of Patents for class 455 subclass 123]    123Automatically controlled:
 This subclass is indented under subclass 121.  Subject matter wherein the tuning is controlled in response to a signal condition.
  
[List of Patents for class 455 subclass 124]    124Distributed parameter device:
 This subclass is indented under subclass 120.  Subject matter where the tuning structure includes, as a significant part thereof, structure with distributed parameter wave transmission circuits or circuits designed to simulate the impedance characteristics of distributed parameter wave transmission circuits.

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333Wave Transmission Lines and Networks,   appropriate subclasses.
  
[List of Patents for class 455 subclass 125]    125Automatic adjustment of tuning:
 This subclass is indented under subclass 120.  Subject matter where the variation or substitution is in response to a characteristic of the transmitter or transmitted signal.
  
[List of Patents for class 455 subclass 126]    126With feedback of modulated output signal:
 This subclass is indented under subclass 91.  Subject matter including provision to apply a portion of the output signal of the transmitter to the input of a prior stage.
(1) Note. The feedback circuit may include an auxiliary pickup coil or antenna to collect a portion of the energy being transmitted.
(2) Note. The signal feedback may be shifted in phase to compensate for hum or distortion.

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69,for a system having a transmitter and receiver at separate stations in which the transmitter is controlled by signal feedback from the receiver.
  
[List of Patents for class 455 subclass 127.1]    127.1Power control, power supply, or bias voltage supply:
 This subclass is indented under subclass 91.  Subject matter including control detail of transmitter power output (e.g., via power amplifiers), or detail of the source of electrical energy, or of the circuitry connecting such source to the transmitter for supplying power, or biasing potential to the active elements of the transmitter.

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117,for power or bias control for transmitter circuit or operator protection.
343,for power or bias voltage supply in receivers.
572,for power supply in transceiver.
  
[List of Patents for class 455 subclass 127.2]    127.2Gain control:
 This subclass is indented under subclass 127.1.  Subject matter including detail of controlling the gain of an active element (such as power amplifier) of the transmitter.

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330Amplifiers,   subclass 278 for gain control means.
  
[List of Patents for class 455 subclass 127.3]    127.3Plural amplifier stages:
 This subclass is indented under subclass 127.2.  Subject matter including detail of controlling the gains of plural amplifier stages of the transmitter.

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330Amplifiers,   appropriate subclasses for amplifiers, per se.
  
[List of Patents for class 455 subclass 127.4]    127.4Dual mode (e.g., analog and digital):
 This subclass is indented under subclass 127.1.  Subject matter including detail of a transmitter operable in either of two modes.

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553.1,for dual mode radiotelephone using more than one transceiver (e.g., for analog and digital, trunking and cellular, etc.).
  
[List of Patents for class 455 subclass 127.5]    127.5Power conservation:
 This subclass is indented under subclass 127.1.  Subject matter including detail of reducing power consumption in a transmitter.

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574,for power conservation in transceiver.

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340Communications: Electrical,   subclass 7.32 for battery saving in code responsive receiver (such as pager).
713Electrical Computers and Digital Processing Systems: Support,   subclasses 320 through 324for computer power conservation.
  
[List of Patents for class 455 subclass 128]    128With casing or housing:
 This subclass is indented under subclass 91.  Subject matter provided with a casing or housing for enclosing the transmitter or a portion of the transmitter.
(1) Note. For classification in this subclass, some detail of the transmitter must be claimed along with the casing or housing.

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174Electricity: Conductors and Insulators,   subclasses 50 through 565for electrical equipment boxes and housings, in general.
220Receptacles,   appropriate subclasses.
312Supports: Cabinet Structure,   subclass 7.1 for radio cabinets, per se.
331Oscillators,   subclasses 67 through 69for oscillators with shielding, casings, or housings.
361Electricity: Electrical Systems and Devices,   subclasses 331+ for housings and mounting assemblies with plural diverse electrical components.
  
[List of Patents for class 455 subclass 129]    129With coupled antenna:
 This subclass is indented under subclass 91.  Subject matter including an antenna and circuit for coupling the antenna to the active elements of the transmitter.
(1) Note. For classification here, some transmitter details should be included in the claimed combination. Combinations of antenna, coupling, and nominal transmitter are classified in Class 343, Communications: Radio Wave, subclasses 850+. See also (4) Note under subclass 850 of Class 343.

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114.1through 114.3, for coupling systems restricted or related to suppression of harmonics.
  
[List of Patents for class 455 subclass 130]    130RECEIVER OR ANALOG MODULATED SIGNAL FREQUENCY CONVERTER:
 This subclass is indented under the class definition.  Apparatus comprising (a) means for receiving a carrier wave, upon which an information signal has been modulated, and deriving the original information signal from the modulated carrier wave. Further means may be provided for converting the derived signal into a physical manifestation readily perceived by at least one of the human senses (e.g., sound) or (b) devices whereby an incoming carrier wave signal, which has been modulated by an analog signal, is changed from one carrier frequency to another carrier frequency.
(1) Note. The system and apparatus found in this and the indented subclasses under (1) above will include wave collection means, at least one wave mixing or modifying means, detector, or demodulator means and utilization means, which utilization means may consist of a sound reproducing device. This class also contains subcombinations of any of the above recited elements combined with coupling circuitry, whereby some function of a complete receiver system is performed; as for example, antenna means broadly plus detector, radio frequency amplifier plus mixer means, etc., and which subcombinations are not elsewhere classifiable.
(2) Note. The apparatus found in this and the indented subclasses will be restricted to those systems which are limited, by claimed subject matter, to use in the reception and utilization of electromagnetic wave energy transmitted in the form of a carrier wave having an analog signal of arbitrary message content modulated thereon or in the form of one or more sidebands, with or without a carrier, resulting from the modulation of a carrier wave by some external source. The modulation may consist of amplitude modulation, frequency, or phase modulation, or any combination thereof. The utilization means will in general comprise loud speaker means but may include visual reproduction means or in some cases a combination of both.
(3) Note. Ordinarily this and the indented subclasses will not include patents whose claimed subject matter includes (a) devices for the operation and control of mechanical devices at a distance by radiant energy, (b) systems and devices for the reception and utilization of facsimile (television) or telegraph signals, (c) systems and devices for the reception of energy which utilize compressional waves in the audible range (telephony), (d) systems and apparatus restricted to the use of radio wave energy which is transmitted to and reflected from some object, the reflected energy being received at a receiving station (i.e., radar), and (e) systems and apparatus for the communication of pulse or digital information.

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74Machine Element or Mechanism,   subclasses 10+ for mechanical dial operators; and see the notes thereto for the electrical type.
178Telegraphy,   and 379, Telephonic Communications, appropriate subclasses for line instruments restricted to use in these arts, particularly Class 178, subclasses 15 , 17, 48, and 88+ for receivers and recorders adapted to code-signalling.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control.
329Demodulators,   appropriate subclasses for demodulators in general and particularly subclasses 315+ for frequency demodulators, subclasses 345+ for phase demodulators, and subclasses 347+ for amplitude demodulators.
330Amplifiers,   appropriate subclasses for radio frequency, intermediate frequency, or audio frequency amplifiers, per se, useful in receivers in this class.
331Oscillators,   appropriate subclasses for electrical oscillator systems of general application, particularly subclasses 1+ for automatic frequency stabilized oscillators; and subclasses 37+ for beat frequency oscillators similar to the frequency conversion stage of a heterodyne type receiver.
334Tuners,   appropriate subclasses for specific adjustable resonant circuits, per se, utilizable as tuners for radio receivers.
343Communications: Radio Wave Antennas,   subclasses 5+ for reflected or otherwise returned wave systems, e.g., radar; and subclasses 100+ for directive radio wave energy systems including receivers; see subclass 113 for direction finding receivers; and subclasses 700+ for antennas which may be used with radio receivers.
370Multiplex Communications,   for modulated carrier wave receivers and systems designed to simultaneously receive a plurality of messages.
375Pulse or Digital Communications,   subclasses 316+ for pulse and digital modulated carrier wave receivers.
398Optical Communications,   various subclasses for optical communication.
714Error Detection/Correction and Fault Detection/Recovery,   subclasses 712+ for diagnostic test of transmission facility.
  
[List of Patents for class 455 subclass 131]    131Frequency conversion between signal source (e.g., wave collector) and receiver:
 This subclass is indented under subclass 130.  Subject matter where the frequency of the signal supplied by the signal source (antenna or cable) is converted to another frequency which the receiver is able to receive.
  
[List of Patents for class 455 subclass 132]    132Plural receivers:
 This subclass is indented under subclass 130.  Subject matter which comprises all of the essential elements (as defined in the definition of subclass 130 above and not merely by name only) of two or more separate receiver means, each of the receiver means being capable of, if detached from or removed from each of the other separate receivers, deriving a useful signal which is representative of useful information carried by an incoming modulated carrier wave and which plural receiver system is not otherwise classifiable.
(1) Note. The subject matter found here may include a plurality of structurally claimed receiver means whose input is derived from separate antenna or collector means, or a plurality of receiver means having some stage in common; for example, a common local oscillator, volume control, or utilization means, provided, that each recited receiver means is capable, if acting along and utilizing the common stage, of deriving a signal representative of the useful information carried by the modulation signal. Systems wherein a plurality of individual receiver means are fed from a single antenna will not be found here but in subclasses 6.1+. For purposes of classification in this subclass a plurality of receivers each receiving its input from a single source are considered to be merely a plurality of output channels for a single carrier wave input even though each of the channels performs the normal function of a complete receiver having a common input means and may be tuned to receive a different wave frequency.
(2) Note. The plurality of receivers found in this and the indented subclasses will generally be located at the same geographical location (as in a rack) or closely adjacent thereto (as in a building or structure), for example, plural nondirectional receivers utilized in a diversity system. The antennas or collecting means may be situated at some distance apart, but in the same general vicinity. To be classified here the plurality of receivers must have some common cooperation or association one with another. For a plurality of receivers located at distant locations relative to each other even though they may be responsive to a particular carrier wave originating at single transmitter the search must be extended to the systems subclasses herein-above in this class or other appropriate classes.
  
[List of Patents for class 455 subclass 133]    133With output selecting:
 This subclass is indented under subclass 132.  Subject matter where output signals from the several receivers are compared and a selected one of the output signals is either (a) applied to a utilization means, or (b) suppressed or prevented from appearing at the utilization means.
  
[List of Patents for class 455 subclass 134]    134By signal strength:
 This subclass is indented under subclass 133.  Subject matter where the output signal is selected according to its amplitude.
  
[List of Patents for class 455 subclass 135]    135By signal quality (e.g., signal to noise ratio):
 This subclass is indented under subclass 133.  Subject matter where the output signals are selected according to a measure of their signal quality.
  
[List of Patents for class 455 subclass 136]    136With control (e.g., automatic gain control, automatic frequency control, etc.):
 This subclass is indented under subclass 133.  Subject matter having provision for controlling an operating characteristic of at least one of the receivers.
  
[List of Patents for class 455 subclass 137]    137With output combining:
 This subclass is indented under subclass 132.  Subject matter where the outputs of two or more of the receivers are combined in an additive manner before being applied to a common utilization means.
  
[List of Patents for class 455 subclass 138]    138With control (e.g., automatic gas control):
 This subclass is indented under subclass 137.  Subject matter where one or more of the operating characteristics of one or more of the receivers is controlled.
  
[List of Patents for class 455 subclass 139]    139Frequency or phase control:
 This subclass is indented under subclass 138.  Subject matter where the frequency or phase of an oscillator in the receiver is controlled.
  
[List of Patents for class 455 subclass 140]    140Selectively actuated or controlled:
 This subclass is indented under subclass 132.  Subject matter where each of the separate receivers may be independently energized, connected to a signal such as an antenna, individually tuned, or otherwise controlled to the exclusion of the others.
  
[List of Patents for class 455 subclass 141]    141Including common stage (e.g., local oscillator):
 This subclass is indented under subclass 132.  Subject matter including one or more local oscillators or other stage which act in common with two or more of the receivers.
  
[List of Patents for class 455 subclass 142]    142Convertible to different type (e.g., AM to FM):
 This subclass is indented under subclass 130.  Subject matter comprising a receiver whose circuit can be changed to receive at least two different types of modulation, for example, amplitude or frequency modulated waves.
(1) Note. Such receivers may be of the superheterodyne type and employ a common pre-amplifier, converter, and intermediate frequency stage for both types of modulation.

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370Multiplex Communications,   appropriate subclasses for digital combined with analog transmission.
375Pulse or Digital Communications,   subclass 216 for digital convertible to/from analog.
  
[List of Patents for class 455 subclass 143]    143With distinct signal path for each type:
 This subclass is indented under subclass 142.  Subject matter where the receiver contains a plurality of separate signal paths, each path being adapted for a different type of modulated signal, between the input and the output of receiver.
(1) Note. An example of the subject matter found here may include separate diverse type collection means followed by a radio frequency stage or stages and a mixer with a common intermediate frequency stage followed by diverse detectors feeding a common audio frequency amplifier.
  
[List of Patents for class 455 subclass 144]    144With dual purpose amplifying or other stage:
 This subclass is indented under subclass 142.  Subject matter including one or more stages which perform plural functions.
(1) Note. Some examples of dual purpose stages are VHF an UHF amplifiers, amplifier and limiter, and AM-FM detector.
  
[List of Patents for class 455 subclass 145]    145Panoramic display:
 This subclass is indented under subclass 130.  Subject matter including a cathode-ray oscilloscope for displaying the received signals.

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1,for transmitters controlled by a spectrum sweeping or panoramic type receiver for transmitting a jamming signal.

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324Electricity: Measuring and Testing,   subclasses 76.12+ for apparatus for the analysis of complex electrical waves and which utilize panoramic display methods.
329Demodulators,   appropriate subclasses for a demodulator including a cathode-ray tube.
343Communications: Radio Wave Antennas,   subclasses 100+ for directive radio wave energy panoramic-type receivers utilized as radio beacons.
  
[List of Patents for class 455 subclass 146]    146Plural separate paths or plural oscillators:
 This subclass is indented under subclass 145.  Subject matter wherein the receiver includes more than one individual circuit path or more than one local oscillator.
(1) Note. For plural separator signal paths, at least a portion of the input carrier wave is conducted to an output utilization means by each path.
(2) Note. For plural oscillators, the output of each oscillator is applied to one of a plurality of mixer or conversion means.

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143,303+ and 313, for other types of receivers having plural signal paths therein.
315+,for plural frequency conversion means with plural local oscillators.
  
[List of Patents for class 455 subclass 147]    147Particular local oscillator control:
 This subclass is indented under subclass 145.  Subject matter wherein the receiver includes particular means whereby the frequency of the local oscillator means is maintained constant or whereby some other operating condition of the oscillator means is controlled.

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164.1,for scanning receivers with automatic frequency control.
173.1,for mechanical or electromechanical frequency selection means with automatic frequency control.
182.1,for channel or station selection with automatic frequency control.
208+,for frequency or phase modulation type receivers with synchronized or controlled local oscillator means.
255+,for automatic frequency control systems for receivers in general.
316,for receivers with frequency conversion means with frequency stabilizing means for the local oscillator.
  
[List of Patents for class 455 subclass 148]    148With oscilloscope sweep signal derivation or control:
 This subclass is indented under subclass 145.  Subject matter wherein the receiver includes particular means for generating or controlling the voltage applied to the oscilloscope (e.g., control of voltage amplitude or cathode-ray beam intensity).

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315Electric Lamp and Discharge Devices: Systems,   subclasses 364+ for cathode-ray tube deflection systems in general, particularly subclasses 383+ for ray beam intensity control.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 131+ for miscellaneous sawtooth or ramp circuit.
331Oscillators,   subclasses 143+ for free running relaxation oscillators utilized as sawtooth generators.
  
[List of Patents for class 455 subclass 149]    149Plural output (e.g., plural speakers) (not stereo):
 This subclass is indented under subclass 130.  Subject matter where the receiver has a plurality of separate outputs.
(1) Note. Stereo receivers are classified in Class 381, subclasses 1+.
  
[List of Patents for class 455 subclass 150.1]    150.1Signal selection based on frequency (e.g., tuning):
 This subclass is indented under subclass 130.  Subject matter comprising means to cause the receiver to respond, selectively, to any one of two or more carrier waves.

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77,for transceivers tuning.
120+,for transmitters with tuning.
340,for receivers in general with adjustable tuning means between stages.

SEE OR SEARCH CLASS:

74Machine Element or Mechanism,   subclasses 10+ for a radio tuner by names only when claimed in combination with shaft positioning means.
324Electricity: Measuring and Testing,   subclasses 76.39+ for systems for measuring the frequency of a cyclic current or voltage by tuning to resonance with a reference source.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 1+ for miscellaneous discriminating circuits and particularly subclasses 39+ for frequency discrimination.
334Tuners,   appropriate subclasses for tuners, per se.
336Inductor Devices,   appropriate subclass for specific type inductor, per se, which may be used in a selective circuit, see particularly subclasses 130+ .
340Communications: Electrical,   subclasses 870.4+ for telemetering systems including selective receivers.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 5+ for radar receivers with wave selecting means and subclasses 100+ for directive receivers with selecting means.
346Recorders,   subclass 37 for the combination of a tuning responsive radio receiver with recording means.
348Television,   subclasses 725+ for television receivers having frequency selecting means.
361Electricity: Electrical Systems and Devices,   subclasses 182+ for electric control circuits for relays which are frequency responsive.
370Multiplex Communications,   appropriate subclass for multiplex receivers with frequency selection means.
375Pulse or Digital Communications,   subclasses 316+ for pulse receivers with frequency selection.
  
[List of Patents for class 455 subclass 151.1]    151.1Remote control of channel or station selection:
 This subclass is indented under subclass 150.1.  Subject matter wherein the tuning means includes a control means that is actuated at a distance from the receiver.

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352+,for remote control of receivers for other than signal selection.

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334Tuners,   subclasses 8+ for remotely controlled tuner which claims significant details of the tuner.
  
[List of Patents for class 455 subclass 151.2]    151.2Wireless link (sonic, RF or infrared):
 This subclass is indented under subclass 151.1.  Subject matter wherein the remote control device is not physically connected to the receiver and generates an acoustic wave, an electromagnetic wave, or a pulse train (e.g., sonic, RF, or infrared).

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340Communications: Electrical,   subclasses 2.1 through 2.8for path selection.
  
[List of Patents for class 455 subclass 151.3]    151.3Remote oscillator tuned:
 This subclass is indented under subclass 151.1.  Subject matter wherein the control means includes an oscillator which generates alternating-current power at a frequency which may be changed at will by the operator.
  
[List of Patents for class 455 subclass 151.4]    151.4Plural electronic devices controlled:
 This subclass is indented under subclass 151.1.  Subject matter wherein the remote control apparatus operates at least two or more receivers.
  
[List of Patents for class 455 subclass 152.1]    152.1Of or combined with vehicle receiver:
 This subclass is indented under subclass 151.1.  Subject matter wherein the receiver system has tuning means in addition to the remote control means and is carried by or combined with a land vehicle (e.g., automobile).

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297,for receiver having noise or interference elimination combined with vehicle structure.
  
[List of Patents for class 455 subclass 153.1]    153.1Mechanical:
 This subclass is indented under subclass 151.1.  Subject matter wherein the receiver includes mechanical means responsive to the remote control device to the carrier wave.
  
[List of Patents for class 455 subclass 153.2]    153.2With wired link:
 This subclass is indented under subclass 153.1.  Subject matter wherein the remote control device is electrically connected to the receiver by a cable or a wire.
(1) Note. Wire may carry current to a motor in the receiver which actuates the mechanical means to vary the frequency response.
  
[List of Patents for class 455 subclass 154.1]    154.1With indication of frequency, channel, or selector condition (e.g., tuning aid):
 This subclass is indented under subclass 150.1.  Subject matter including means for making a condition pertaining to the tuning of the receiver perceptible to a human operator.
(1) Note. This subclass and the indented subclass may also include TV tuning or channel indicators wherein the TV receiver is broadly claimed which does not include any particular TV processing circuitry, e.g., horizontal or vertical sync circuitry, etc.

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115.1through 115.4, for transmitters with tuning indicator.
145+,for receivers with panoramic display.

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74Machine Element or Mechanism,   subclasses 10+ for mechanical radio tuning mechanisms which may include dial indication means.
116Signals and Indicators,   subclasses 241+ for radio tuning indicators.
324Electricity: Measuring and Testing,   subclasses 76.11+ for devices for measuring or testing electricity, per se, and having indication means, particularly indented subclasses 76.49 and 76.51 for frequency measuring systems employing tuned circuits.
329Demodulators,   subclasses 315+ for frequency detectors with indication means.
331Oscillators,   subclass 64 for oscillator devices with indicating means.
334Tuners,   appropriate subclasses for tuning devices, per se, with indicating means.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 350+ for directive radio energy receivers with indicating means.
345Computer Graphics Processing and Selective Visual Display Systems,   subclasses 1.1 through 111for visual display systems with selective electrical control.
348Television,   subclasses 569+ for television receivers with tuning indicators.
381Electrical Audio Signal Processing Systems and Devices,   subclass 12 for stereo receivers with indicators.
  
[List of Patents for class 455 subclass 154.2]    154.2Scanning display:
 This subclass is indented under subclass 154.1.  Subject matter having means to automatically and continuously varies the carrier wave frequency to which the receiver is tuned and means to continuously display the frequency.
  
[List of Patents for class 455 subclass 155.1]    155.1By meter:
 This subclass is indented under subclass 154.1.  Subject matter comprising a movable visual indication actuated by electromagnetic means.
  
[List of Patents for class 455 subclass 156.1]    156.1Audible indicator:
 This subclass is indented under subclass 154.1.  Subject matter comprising means to generate a specific tone or sound or to vary the normal sound output of the receiver.
  
[List of Patents for class 455 subclass 157.1]    157.1Analog frequency indication (e.g., dial):
 This subclass is indented under subclass 154.1.  Subject matter including means for indicating the frequency value of the carrier wave to which the receiver is adjusted or tuned (e.g., tuning dial with a pointer).

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67.11through 67.7, for transmitters and receivers at separate stations with measuring, testing, and monitoring which may include the frequency display of the receiver.
226.1,for receiver measuring, testing, and calibration apparatus which may include means for displaying the actual receiver tuned frequency.
  
[List of Patents for class 455 subclass 157.2]    157.2With light indication or bar type:
 This subclass is indented under subclass 157.1.  Subject matter wherein the perceptible means is a line divided into equal measures which is variably illuminated to indicate the condition.
  
[List of Patents for class 455 subclass 158.1]    158.1Channel index indication:
 This subclass is indented under subclass 154.1.  Subject matter wherein the indication means displays information pertaining to the identity of the channel or station to which the receiver is tuned.

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345Computer Graphics Processing and Selective Visual Display Systems,   subclasses 168+ for keyboard input for a visual display system with selective electrical control, and subclasses 33+ and 467-472.3 for particular types of character displays in a visual display system with selective electrical control.
348Television,   subclasses 569+ for TV receivers which may include channel number displays.
  
[List of Patents for class 455 subclass 158.2]    158.2With electronic digital indication:
 This subclass is indented under subclass 158.1.  Subject matter wherein the display means is an electronic means for visually representing the channel or station number (e.g., seven-segment numerical display).
  
[List of Patents for class 455 subclass 158.3]    158.3Using a counter:
 This subclass is indented under subclass 158.2.  Subject matter wherein the electronic means includes a counter which counts control pulses transmitted by the remote control device to cause the receiver to be tuned from channel to channel.

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377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   appropriate subclasses for pulse counting means, per se.
  
[List of Patents for class 455 subclass 158.4]    158.4With multiple display functions:
 This subclass is indented under subclass 158.1.  Subject matter wherein the channel index indicating means also displays another kind of information (e.g., time of day, frequency, stereo mode, etc.).
  
[List of Patents for class 455 subclass 158.5]    158.5Non-numeric display (e.g., call letters):
 This subclass is indented under subclass 158.1.  Subject matter wherein the channel index indication includes alphanumeric data about a received channel.
  
[List of Patents for class 455 subclass 159.1]    159.1Variable light indication:
 This subclass is indented under subclass 154.1.  Subject matter which the condition is indicated by a variable light source.
(1) Note. The variable light indication source may be an electron beam "ray" tube or LED by which tuning may be adjusted correctly.
  
[List of Patents for class 455 subclass 159.2]    159.2Plural lamps:
 This subclass is indented under subclass 159.1.  Subject matter wherein the variable light indicator contains at least two or more light sources.
  
[List of Patents for class 455 subclass 160.1]    160.1Plural tuning modes (e.g., manual and scanning, etc.):
 This subclass is indented under subclass 150.1.  Subject matter having two or more signal selection means (e.g., manual and automatic scanning and means to selectively actuate one of the signal selection means).
(1) Note. This subclass is restricted to plural discrete selection modes. Systems such as coarse tuning and fine tuning are excluded.

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161.1+,for frequency scanning receivers.
170.1+,for receivers with manual, mechanical,or electromechanical selection.
173.1,182.3, and 192.3 for systems such as coarse tuning and fine tuning.
179.1+,for channel or station selection receivers.
188.1+,for band selection receivers.
  
[List of Patents for class 455 subclass 161.1]    161.1Frequency scanning:
 This subclass is indented under subclass 150.1.  Subject matter in which the selection means includes means for automatically tuning the receiver through a desired frequency range or a plurality of frequency ranges to obtain a carrier signal having predetermined characteristics (e.g., frequency, amplitude).
(1) Note. The selection means in this subclass and the indented subclasses may include electrical, mechanical, or electromechanical systems. For example, the selection means may be adjusted to resonance at a desired frequency automatically by the action of a manually operated button, lever, dial, or knob means or means whereby the selection means is locked or clamped in a predetermined position as a consequence of the frequency of the received input carrier signal.

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32,for receiver selection with scanning.
77,for transceivers with automatic tuning.
125,for transmitters with automatic adjustment of tuning.
145,for panoramic receivers with frequency scanning.

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324Electricity: Measuring and Testing,   subclasses 76.12+ for frequency spectrum analyzers using scanning receivers.
348Television,   subclass 734 for television receivers with search tuning.
  
[List of Patents for class 455 subclass 161.2]    161.2With processor control:
 This subclass is indented under subclass 161.1.  Subject matter wherein the means includes a programmable controller for automatically tuning the receiver through the desired frequency range.
  
[List of Patents for class 455 subclass 161.3]    161.3Using signal strength or quality:
 This subclass is indented under subclass 161.1.  Subject matter wherein the predetermined characteristic is the strength of the information signal or the signal-to-noise ratio.
  
[List of Patents for class 455 subclass 162.1]    162.1Motor activated:
 This subclass is indented under subclass 161.1.  Subject matter in which the selection means is controlled by a motor.

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170.1+,for signal selection receivers employing mechanical or electromechanical selection means such as a motor, particularly subclass 172.1 for time activated receiver selection combined with a motor.

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318Electricity: Motive Power Systems,   appropriate subclasses for generic motor control device.
334Tuners,   subclasses 20+ for motor operated band scanning or selector circuit for tuners, per se.
  
[List of Patents for class 455 subclass 163.1]    163.1Reversible motor (e.g., end-stop control):
 This subclass is indented under subclass 162.1.  Subject matter in which the motor is bidirectional and circuit means is provided for controlling the direction of operation.
(1) Note. This subclass provides for selective receivers in which the tuning means has limitations in motion and cam or other actuating means controls the motor circuit to prevent damage.

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318Electricity: Motive Power Systems,   subclass 626 for limit or end-stop control of an electric motor in a servo system and subclasses 280+ for motor reversing systems.
  
[List of Patents for class 455 subclass 164.1]    164.1With automatic frequency control:
 This subclass is indented under subclass 161.1.  Subject matter including a self-regulating control circuit in the receiver which compensates for small variations in a carrier signal frequency to provide a stable audio output.

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75,for transceivers with frequency stabilization.
119,for transmitters with automatic frequency control.
173.1,for manual, mechanical, or electromechanical frequency selection means with automatic frequency control.
182.2,for channel or station selection with automatic frequency control.
192.2,for receiver tuning in general with automatic frequency control or fine tuning control.
257,for nontuning receivers with automatic frequency control.

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331Oscillators,   subclasses 1+ for oscillators having automatic frequency control.
348Television,   subclass 735 for television receivers with automatic frequency control.
  
[List of Patents for class 455 subclass 164.2]    164.2Processor controlled (AFC):
 This subclass is indented under subclass 164.1.  Subject matter wherein the automatic frequency control is controlled by a programmable controller.
(1) Note. The processor may be a microprocessor.
  
[List of Patents for class 455 subclass 165.1]    165.1With frequency synthesizer:
 This subclass is indented under subclass 161.1.  Subject matter wherein the selection means includes means for deriving a plurality of local oscillator frequencies from a variable frequency oscillator by frequency multiplication or division.

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76,for transceivers with frequency synthesizers.
183.1,for channel or station selection with frequency synthesizers.
260,for automatic frequency control receivers with frequency synthesizers.

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331Oscillators,   subclasses 1+ for automatic oscillator frequency control, particularly subclass 1 for oscillator frequency control circuits with particular logic elements (e.g., programmable divider in a phase locked loop).
  
[List of Patents for class 455 subclass 166.1]    166.1With channel skipping selection:
 This subclass is indented under subclass 161.1.  Subject matter including means to cause pass over of certain carrier frequencies during the scanning process.

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175.1,for manual, mechanical, or electromechanical frequency selection means with channel preset.
  
[List of Patents for class 455 subclass 166.2]    166.2With priority channel selection:
 This subclass is indented under subclass 166.1.  Subject matter wherein the channel skipping selection includes means to cause the selection of preferred carrier frequencies over other carrier frequencies.

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179.1,which may include preferred channel selection.
  
[List of Patents for class 455 subclass 167.1]    167.1With dual sweeping:
 This subclass is indented under subclass 161.1.  Subject matter including a plurality of means (e.g., two sweeping oscillators) operating in sequence to cause receiver scanning.
  
[List of Patents for class 455 subclass 168.1]    168.1Multiband:
 This subclass is indented under subclass 161.1.  Subject matter including means for scanning the receiver over a plurality of frequency bands.

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176.1,for manual, mechanical, or electromechanical frequency selection means combined with band selection.
180.1,for channel selection combined with band selection.
188.1+,for general band selection circuits.

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334Tuners,   subclasses 18+ for band scanning used in an electromagnetic operated tuner.
  
[List of Patents for class 455 subclass 169.1]    169.1With particular variable voltage or current tuning:
 This subclass is indented under subclass 161.1.  Subject matter including particular means for providing a changeable voltage or current to a receiver oscillator for scanning.
(1) Note. Some significant detail of the voltage or current supply of receiver oscillator scanning must be claimed for classification in this subclass.

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195.1,for signal selection systems in general using variable voltage or current tuning.

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334Tuners,   subclasses 11+ for particular variable voltage or current responsive tuners.
  
[List of Patents for class 455 subclass 169.2]    169.2With varactor diode:
 This subclass is indented under subclass 169.1.  Subject matter wherein the particular variable voltage or current tuning means includes a two-terminal semiconductor device capacitance varies with the applied voltage.
  
[List of Patents for class 455 subclass 170.1]    170.1With mechanical or electromechanical selection:
 This subclass is indented under subclass 150.1.  Subject matter including mechanical or electromechanical operating devices (e.g., knobs, push buttons, tuning shafts, movable cores, ganged elements, etc.) for tuning the receiver.

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120+,for transmitter tuning which may include manual, mechanical, or electromechanical means for frequency selection.
160.1,for receivers comprising plural selection modes which may include manual, mechanical, or electromechanical selection means.
161.1+,for frequency scanning receivers which may include manual, mechanical, or electromechanical means for frequency selection.

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74Machine Element or Mechanism,   subclasses 10+ for mechanical radio tuning mechanisms.
334Tuners,   appropriate subclasses for mechanical or electromagnetic type tuners.
  
[List of Patents for class 455 subclass 171.1]    171.1Time actuated:
 This subclass is indented under subclass 170.1.  Subject matter wherein the mechanical or electromechanical selection means is controlled by a timing device (e.g., clock).

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181.1,for channel or station selection which is controlled or programmed by a timing device.
231,for receiver combined with diverse device, such diverse device being a clock.

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368Horology: Time Measuring Systems or Devices,   appropriate subclasses for particular clock structure.
  
[List of Patents for class 455 subclass 172.1]    172.1Including a motor:
 This subclass is indented under subclass 171.1.  Subject matter wherein the selection means is done by an electric motor.

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162.1,for motor activated frequency scanning receivers.

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334Tuners,   subclasses 20+ for motor activated band scanning or selector circuit for tuners, per se.
  
[List of Patents for class 455 subclass 173.1]    173.1With automatic frequency control of fine tuning:
 This subclass is indented under subclass 170.1.  Subject matter wherein the manual, mechanical, or electromechanical means includes means for automatically stabilizing a receiver local oscillator frequency or means to permit fine adjustment of the local oscillator to the carrier frequency of a signal.

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75,for transceivers with frequency stabilization (e.g., AFC).
119,for transmitters with automatic carrier frequency stabilization.
164.1+,for frequency scanning receivers with automatic frequency control.
182.1+,for channel or station selection receivers with automatic frequency control or fine tuning control.
192.1+,for signal selection in general with automatic frequency control or fine tuning control.
255,for nontuning receivers with automatic frequency control.

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334Tuners,   subclasses 13 , 16, and 26+ for tuners with automatic frequency centering circuits.
  
[List of Patents for class 455 subclass 174.1]    174.1With muting (e.g., silent tuning):
 This subclass is indented under subclass 170.1.  Subject matter including means for silencing the receiver at all times except when the signal selection means is exactly adjusted to the desired carrier frequency.

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194.1+,for signal selection receivers (nonmechanical type) with muting.
212+,for FM receivers with muting or squelch circuits.
218+,for receivers in general with muting or squelching circuits.
  
[List of Patents for class 455 subclass 175.1]    175.1With carrier wave preset:
 This subclass is indented under subclass 170.1.  Subject matter including means for preselecting a desired carrier wave frequency (e.g., by push buttons).

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160.1,for receivers with plural signal selection modes wherein at least one such mode may be a preset signal selection mode.
166.1+,for frequency scanning receivers which may comprise means for preselecting a channel to be skipped or a priority channel to be monitored.
186.1+,for channel or station selection receivers with means for programming predetermined channel information into a storage memory.

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334Tuners,   subclass 29 for tuners with predetermined center frequency selectors.
  
[List of Patents for class 455 subclass 176.1]    176.1Combined with band selection:
 This subclass is indented under subclass 170.1.  Subject matter including means for selecting one of a plurality of carrier wave bands.

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168.1,for multiband frequency scanning receivers.
180.1,for channel or station selection receivers combined with band selection.
188.1+,for band selection receivers in general.

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334Tuners,   subclasses 18+ for band selector with electromagnetic operator.
  
[List of Patents for class 455 subclass 177.1]    177.1Combined with other control (e.g., bandwidth, volume, gain, etc.):
 This subclass is indented under subclass 170.1.  Subject matter including additional means for controlling other functions of the receiver (e.g., bandwidth, volume, gain, etc.).

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200.1,for nonmechanical or nonelectromechanical-type frequency selection receivers with other control.
232+,for receivers in general with gain, level, or volume control.
266,for receivers with selectivity or bandwidth control.
  
[List of Patents for class 455 subclass 178.1]    178.1With plurality of tunable circuits:
 This subclass is indented under subclass 170.1.  Subject matter including separate circuits each being adjustable by the operation of manual, mechanical, or electromechanical means (e.g., tuning shaft).

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187.1,for channel or station selection receivers using separate tuned circuits for each channel or station.
191.1+,for band selection receivers with plural tuned circuits or tunable coupled stages.

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334Tuners,   subclass 2 for plural diverse type tuners and subclasses 42+ for resonant line element tuners employing plural operated tuning units.
  
[List of Patents for class 455 subclass 179.1]    179.1Channel or station selection:
 This subclass is indented under subclass 150.1.  Subject matter including means to tune the receiver to a desired carrier wave frequency.
(1) Note. This subclass and the indented subclasses may also include TV channel or station selections wherein the TV receiver is broadly claimed and does not include any particular TV processing circuitry, e.g., horizontal and vertical sync, circuitry, etc.

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73+,for transceivers which may include channel selection means.
151.1,for remote control of channel or station selection.
160.1,for receivers with plural selection modes which may include channel selection means.
161.1+,for frequency scanning receivers which may include channel selection means, particularly subclasses 166.1+ for channel skipping or priority channel selection.
170.1+,for receivers with mechanical or electromechanical selection which may include channel selection means.

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334Tuners,   appropriate subclasses for tuners, per se, with channel or station selection means.
348Television,   subclasses 570 and 731+ for television channel or station selections with such particular processing circuitry.
  
[List of Patents for class 455 subclass 180.1]    180.1Combined with band selection:
 This subclass is indented under subclass 179.1.  Subject matter including means in addition to the channel selection means for selecting a desired frequency range from a plurality of frequency ranges, whereby a channel frequency can be selected from such desired frequency range.

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77,for transceivers with tuning which may include band selection means.
168.1,for frequency scanning receivers with band selection means.
176.1,for receivers with mechanical or electromechanical selection means combined with band selection.
188.1+,for band selection receivers in general.

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348Television,   subclasses 570 and 731+ for TV tuning which may include band selection means (e.g., UHF, VHF).
  
[List of Patents for class 455 subclass 180.2]    180.2UHF and VHF:
 This subclass is indented under subclass 180.1.  Subject matter wherein the desired frequency range is within 30 to 3000 MHz.

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188.2,for band selection receivers in general which include UHF and VHF band.
  
[List of Patents for class 455 subclass 180.3]    180.3With phase locked loop (PLL) tuning:
 This subclass is indented under subclass 180.2.  Subject matter wherein the tuning means includes a tuning circuit whose output locks onto and tracks a reference signal for tuning the desired frequency.
(1) Note. Phase locking is accomplished by comparing the phase of an output signal and the reference signal, and then converting any difference into a correction voltage that changes the phase of output so it matches that of the reference or the input signal.
  
[List of Patents for class 455 subclass 180.4]    180.4Varactor tuned (e.g., varactor diode):
 This subclass is indented under subclass 180.2.  Subject matter including a two-terminal semiconductor device capacitance for tuning the desired channel or station frequency.
  
[List of Patents for class 455 subclass 181.1]    181.1Time controlled:
 This subclass is indented under subclass 179.1.  Subject matter wherein the channel or station selection means is activated or programmed by a timing device (e.g., clock).

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171.1,for receivers with manual, mechanical, or electromechanical selection means controlled by a timing device.
  
[List of Patents for class 455 subclass 182.1]    182.1With frequency control:
 This subclass is indented under subclass 179.1.  Subject matter wherein the channel or station selection includes a local oscillator and a control means for stabilizing the oscillator frequency.

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75,for transceiver with frequency stabilization.
164.1+,for frequency scanning receivers with automatic frequency control.
173.1,for receivers with mechanical or electromechanical frequency selection means using AFC or fine tune control.
192.1+,for signal selection with AFC or fine tuning control.
257+,for receivers in general with automatic frequency control.
  
[List of Patents for class 455 subclass 182.2]    182.2Automatic (AFC):
 This subclass is indented under subclass 182.1.  Subject matter wherein the control means is a self-regulating control circuit in the receiver which compensates for small variations in a carrier signal frequency to provide a stable audio output.

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348Television,   subclass 735 for television receiver with automatic frequency control.
  
[List of Patents for class 455 subclass 182.3]    182.3Fine tuning:
 This subclass is indented under subclass 179.1.  Subject matter wherein the channel or station selection means includes a local oscillator and means to permit fine adjustment (either manually or automatically, i.e., AFT) of the oscillator frequency.
  
[List of Patents for class 455 subclass 183.1]    183.1With frequency synthesizer:
 This subclass is indented under subclass 179.1.  Subject matter including means for deriving a plurality of local oscillator frequencies from a variable frequency oscillator by frequency multiplication or division.

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76,for transceivers with frequency synthesizers.
165.1,for frequency scanning receivers with frequency synthesizers.
260,for automatic frequency control receivers with frequency synthesizers.

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331Oscillators,   subclass 1 for oscillator frequency control circuits with particular logic elements (e.g., programmable divider in a phase locked loop).
  
[List of Patents for class 455 subclass 183.2]    183.2Processor controlled:
 This subclass is indented under subclass 183.1.  Subject matter wherein the frequency synthesizer includes a programmable controller for selecting an appropriate one of the local oscillator frequencies to tune the receiver to the desired channel or station.
  
[List of Patents for class 455 subclass 184.1]    184.1With comparing desired and existing tuning conditions:
 This subclass is indented under subclass 179.1.  Subject matter including comparison means for determining the difference between the carrier wave to which the receiver is current tuned and a newly selected carrier wave.

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161.1+,for frequency scanning receivers which may include comparison means.
170.1+,for manual, mechanical, or electromechanical frequency selection which may also include comparison means.
  
[List of Patents for class 455 subclass 185.1]    185.1With channel information storage:
 This subclass is indented under subclass 179.1.  Subject matter including means for storing about the channel to which the receiver is tuned.
(1) Note. This subclass may include a digital memory for storing channel number representation or a storage capacitor for storing channel voltage.

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77+,for transceiver tuning which may include channel information storage.
161.1+,for frequency scanning receivers which may include channel information storage.
  
[List of Patents for class 455 subclass 186.1]    186.1With memory control or programming:
 This subclass is indented under subclass 185.1.  Subject matter including means for controlling the address or readout of the storage means.

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365Static Information Storage and Retrieval,   appropriate subclasses for generic memory device, particularly subclasses 185.01+ for floating gate memory storage (e.g., flash memory).
  
[List of Patents for class 455 subclass 186.2]    186.2Having a keyboard:
 This subclass is indented under subclass 186.1.  Subject matter wherein the controlling means includes an array of push-button switches with related functions for programming the channel information.

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200Electricity: Circuit Makers and Breakers,   appropriate subclasses for generic switches.
341Coded Data Generation or Conversion,   subclasses 22+ for bodily actuated code generator including keyboard or keypad.
  
[List of Patents for class 455 subclass 187.1]    187.1Separate tuned circuits for each channel or station:
 This subclass is indented under subclass 179.1.  Subject matter including a plurality of separate and distinct circuit means each of which is tuned or tunable to resonate at a particular frequency corresponding to the frequency of a modulated carrier wave channel.
(1) Note. Each of the plurality of circuit means may be preadjusted to be resonant at the carrier frequency of a separate transmitting station and may be selectively inserted into the system at random or in a sequential order.

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178.1,for receivers with manual, mechanical, or electromechanical selection means using a plurality of tunable circuits.

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334Tuners,   appropriate subclasses, especially subclass 7 for push button-type tuners utilizing a plurality of tuned selector circuits.
  
[List of Patents for class 455 subclass 188.1]    188.1Band selection:
 This subclass is indented under subclass 150.1.  Subject matter including means for selecting ranges of radio frequencies lying between specified sets of limits, each range including one or more carrier wave channels.

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77+,for transceiver tuning which may include band selection means.
168.1,for multiband frequency scanning receivers which may include band selection means.
176.1,for mechanical or electromechanical frequency selection receivers combined with band selection.
180.1,for channel or station selection receivers combined with band selection.

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324Electricity: Measuring and Testing,   subclasses 76.39+ for frequency measuring systems which may include band changing or selection means.
334Tuners,   appropriate subclasses for tuners with band selection or changing means.
342Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation),   subclasses 350+ for directive radio energy receivers which may include band selection means.
348Television,   subclasses 570 and 731+ for TV tuning receivers which may include band selection means.
370Multiplex Communications,   appropriate subclass for multiplex receivers which may include band selection means.
  
[List of Patents for class 455 subclass 188.2]    188.2UHF and VHF:
 This subclass is indented under subclass 188.1.  Subject matter wherein the frequency range is within 30 to 3000 MHz.
  
[List of Patents for class 455 subclass 189.1]    189.1With plural separate mixer or converter circuits:
 This subclass is indented under subclass 188.1.  Subject matter including two or more separate and distinct means for generating an output signal equal to the sum or difference of a local oscillator frequency and the carrier wave frequency or means for converting the carrier wave frequency to some other frequency by combining it with another frequency.
(1) Note. The separate conversion means may be in separate signal channel paths for providing separate intermediate frequency outputs or may provide input signals for a common intermediate frequency channel.

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22,for radio repeaters with plural conversion stages.
146,for panoramic receivers which may comprise plural separate mixers or converter circuits.
168.1,for frequency scanning receivers which may comprise plural separate mixers or conversion circuits.
176.1,for manual, mechanical, or electromechanical signal selection combined with band selection which may include plural frequency conversion means.
180.1,for channel or station selection receivers combined with band selection means which may comprise plural frequency conversion circuits.
207,for frequency modulation receivers with plural conversion means.
314+,for receivers with frequency conversion systems comprising a plurality of plural separate successive conversion means.
  
[List of Patents for class 455 subclass 190.1]    190.1With frequency conversion:
 This subclass is indented under subclass 188.1.  Subject matter including means for converting the carrier wave frequency to some other frequency by combining it with another frequency.
(1) Note. The converting means may, for example, be a separate frequency band converter, connected between the antenna and the receiver input for adapting a receiver operative in one frequency band (e.g., VHF) to receive signals in another frequency band (e.g., UHF).

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142+,for systems wherein a receiver adapted to receive a wave containing a first type modulation component has means to convert it to receive a wave containing a second type modulation component or vice versa (e.g., AM or FM).
  
[List of Patents for class 455 subclass 191.1]    191.1With plurality of tuned circuits:
 This subclass is indented under subclass 188.1.  Subject matter including two or more tuned circuits each tunable to a different frequency.
(1) Note. The separate tuned circuits need not consist of separate distinct physical elements, but any two or more may share one or more elements in common. As an example, a single inductance may be divided into sections with one or more sections being parallel connected with a capacitor whereby each of the sections when so connected constitutes a separate tuned circuit. The plurality of tuned circuits may be situated either in the input to or the output of a radio frequency amplifier.

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340,for receivers in general with tunable or adjustable coupling circuits between stages.

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334Tuners,   appropriate subclasses for band selecting tuners, per se.
  
[List of Patents for class 455 subclass 191.2]    191.2Varactor tuned:
 This subclass is indented under subclass 191.1.  Subject matter wherein the plurality of tuned circuits includes a two-terminal semiconductor capacitive device for tuning a desired frequency range.
  
[List of Patents for class 455 subclass 191.3]    191.3With switching between stages:
 This subclass is indented under subclass 191.1.  Subject matter wherein the plurality of tuned circuits includes a mechanical or electrical device that completes or breaks a signal path or sends the signal over a different path.
  
[List of Patents for class 455 subclass 192.1]    192.1With frequency control:
 This subclass is indented under subclass 150.1.  Subject matter including a control means for stabilizing a receiver local oscillator frequency.

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75,for transceivers with automatic frequency control.
119,for transmitters with automatic frequency control.
164.1,for frequency scanning receivers with automatic frequency control.
182.1+,for channel or station selection receivers with frequency control.
255,for nontuning receivers with automatic frequency control.
  
[List of Patents for class 455 subclass 192.2]    192.2Automatic (AFC):
 This subclass is indented under subclass 192.1.  Subject matter wherein the control means is a self-regulating control circuit in the receiver which compensates for small variations in a carrier signal frequency to provide a stable audio output.

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164.1,for frequency scanning receivers with automatic frequency control.
173.1,for receivers with mechanical or electromechanical frequency selection means using AFC or fine tuning control.
182.2,for channel or station selection receivers with automatic frequency control.

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348Television,   subclass 735 for television receiver with automatic frequency control.
  
[List of Patents for class 455 subclass 192.3]    192.3Fine tuning:
 This subclass is indented under subclass 192.1.  Subject matter wherein the control means includes means to permit fine adjustment (either manually or automatically, i.e., AFT) of the local oscillator to the carrier frequency of a desired signal.

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173.1,for receivers with mechanical or electromechanical frequency selection means using AFC or fine tuning control.
182.3,for channel or station selection receivers with manual or automatic fine tuning.
  
[List of Patents for class 455 subclass 193.1]    193.1With antenna circuit tuning:
 This subclass is indented under subclass 150.1.  Subject matter wherein the signal selection means comprises a tunable RF circuit coupled to a carrier wave reception means.

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121+,for tunable transmitters with tuning means in the antenna circuit.
275,for receivers with plural antennas and including frequency selecting means.
289,for receivers with tunable coupling means between the antenna and receiver input.
  
[List of Patents for class 455 subclass 193.2]    193.2With plural resonant circuits:
 This subclass is indented under subclass 193.1.  Subject matter wherein the tunable antenna circuit includes a plurality circuits which contain both inductance and capacitance and are therefore tuned to a resonance at a certain frequency.
  
[List of Patents for class 455 subclass 193.3]    193.3Including varactor diode:
 This subclass is indented under subclass 193.1.  Subject matter wherein the tunable RF circuit includes a two-terminal semiconductor capacitive device.
  
[List of Patents for class 455 subclass 194.1]    194.1With muting (e.g., silent tuning):
 This subclass is indented under subclass 150.1.  Subject matter comprising a means to silence the receiver while it is being tuned to the desired carrier frequency (e.g., silent tuning).

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174.1,for mechanical or electromechanical signal selection receivers with muting means.
212,for frequency or phase modulation receivers having squelch circuits or other output silencing.
218,for receivers having squelch in general.
  
[List of Patents for class 455 subclass 194.2]    194.2Amplifier controlled:
 This subclass is indented under subclass 194.1.  Subject matter wherein the means includes an amplifier in a received signal path whose gain is controlled in such a manner that the audio output is muted during the silent tuning.
  
[List of Patents for class 455 subclass 195.1]    195.1Variable voltage or current tuning:
 This subclass is indented under subclass 150.1.  Subject matter wherein the means to select the carrier wave frequency is responsive to voltage or current.
(1) Note. Some significant detail of the voltage or current supply for carrier signal selection must be claimed for classification in this subclass.

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169.1+,for frequency scanning receivers with particular variable voltage or current tuning.

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334Tuners,   subclasses 11+ for particular variable voltage or current responsive tuners.
  
[List of Patents for class 455 subclass 196.1]    196.1Including variation of local oscillator frequency:
 This subclass is indented under subclass 150.1.  Subject matter which includes a variable frequency source of unmodulated oscillation.
(1) Note. Signal frequency selection effected by frequency variation of the oscillation source is classified herein.

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320,for a frequency converter with a local oscillator in which the coupling means is variably tuned.
  
[List of Patents for class 455 subclass 197.1]    197.1By simultaneous control with signal selection:
 This subclass is indented under subclass 196.1.  Subject matter in which the local oscillator frequency and the carrier wave frequency are varied by a common actuator.
  
[List of Patents for class 455 subclass 197.2]    197.2Variable capacitor tuned:
 This subclass is indented under subclass 197.1.  Subject matter comprising an RF tuned circuit and an oscillator tuned circuit, each containing a variable capacitor which is tuned by the common actuator.
  
[List of Patents for class 455 subclass 197.3]    197.3Including additional tuning circuit:
 This subclass is indented under subclass 197.2.  Subject matter including more than two resonant circuits in combination with an additional resonant circuit having a variable capacitor which is varied by the common actuator.
  
[List of Patents for class 455 subclass 198.1]    198.1Including distributed parameter control device:
 This subclass is indented under subclass 197.1.  Subject matter wherein the means to select either the carrier wave or the local oscillator frequency is of the electromagnetic wave transmission type (e.g., resonators, waveguides).

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333Wave Transmission Lines and Networks,   appropriate subclasses for such distributed parameter devices and networks.
334Tuners,   subclasses 41+ for tuners having resonant line elements.
  
[List of Patents for class 455 subclass 199.1]    199.1Discrete frequency types (e.g., channel switching):
 This subclass is indented under subclass 197.1.  Subject matter in which the frequency selection means selects distinct, spaced apart, frequencies.

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179.1,for similar signal selectors absent local oscillator frequency variation.
  
[List of Patents for class 455 subclass 200.1]    200.1With other control (e.g., volume, gain, bandwidth, etc.):
 This subclass is indented under subclass 150.1.  Subject matter including significant details of the signal selection means combined with at least one other functional control means.
(1) Note. To complete the field of search in this class for subject matter found in this subclass, and in which the said other control means is included in some detail, further search must be made in the appropriate subclass relating to the particular control means.
(2) Note. Wherein the subject matter claimed includes two or more type of control means equally claimed as to significant details classification will be in the subclass relating to the particular control means which is highest in the schedule. For example, wherein volume control and tuning control are both claimed with equal particularity, classification will be in subclass 200 with an official cross-reference in subclass 233, etc.

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177.1,for manual, mechanical, or electromechanical type signal selection receivers with other control means.
232+,for gain or volume control means.
233,for volume control means combined with other control means.
255+,for local oscillator frequency control systems.
256,for frequency control combined with other control means which other means may be tuning or wave selection control.
266,for selectivity control wherein the frequency bandwidth is controlled for any desired carrier wave received.
353,for remote control means controlling a plurality of conditions from a remote position.

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334Tuners,   appropriate subclasses for tuners, per se, which may be combined with other control means mechanically.
  
[List of Patents for class 455 subclass 201]    201Exalted carrier:
 This subclass is indented under subclass 130.  Subject matter relating to a receiver system adapted to derive an output voltage representative of useful information modulated upon a carrier wave and comprising means whereby the carrier component is separated from the sideband or bands, amplified and recombined with the sideband or bands for the purpose of preventing the effects of selective fading or for obtaining a relatively undistorted output.

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296,for receiver systems in general having noise or other interference elimination.

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329Demodulators,   subclass 358 for a synchronous amplitude demodulator.
  
[List of Patents for class 455 subclass 202]    202Suppressed carrier:
 This subclass is indented under subclass 130.  Subject matter relating to a receiver system adapted to derive an output voltage representative of useful information modulated upon a carrier wave in the form of amplitude modulation, the carrier portion of the resultant wave being reduced in amplitude at the transmitter with only one or both of the sideband signals being transmitted to the receiver.

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46,for transmitter and receiver systems of the suppressed carrier type.

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375Pulse or Digital Communications,   subclass 270 for transmitter and receiver systems with suppressed carrier; subclass 301 for transmitters with suppressed carrier and subclass 321 for receivers with suppressed carrier.
  
[List of Patents for class 455 subclass 203]    203Carrier and single sideband:
 This subclass is indented under subclass 130.  Subject matter relating to a receiver system adapted to derive an output voltage representative of useful information being transmitted by means of the carrier and one sideband only.

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47,for transmitter and receiver systems of the single sideband type.

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375Pulse or Digital Communications,   subclass 270 for transmitter and receiver systems with single sideband; subclass 301 for single sideband transmitters and subclass 321 for single sideband receivers.
  
[List of Patents for class 455 subclass 204]    204Vestigial sideband:
 This subclass is indented under subclass 130.  Subject matter relating to a receiver system adapted to derive an output voltage representative of useful information modulated upon a carrier wave, the information having been transmitted via a signal comprising a carrier and one normal sideband the other sideband having been largely but not completely suppressed.

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47,for transmitter and receiver vestigial sideband systems.

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348Television,   subclasses 725+ for TV receivers which may include vestigial sideband.
375Pulse or Digital Communications,   subclass 270 for transmitter and receiver pulse systems with vestigial sideband; subclass 301 for vestigial sideband pulse transmitters and subclass 321 for vestigial sideband pulse receivers.
  
[List of Patents for class 455 subclass 205]    205Frequency or phase modulation:
 This subclass is indented under subclass 130.  Subject matter comprising a receiver system designed to convert a frequency-modulated or phase-modulated carrier wave input into perceptible output signals representative of the useful information contained in the modulation signal.
(1) Note. The basic elements of receivers included in this and the indented subclasses includes an input means (e.g., an antenna or converter means, intermediate frequency amplifier means, limiter means, frequency or phase discriminator and/or demodulator means, low (e.g., audio) frequency amplifier means and utilization means such as a loud speaker.
(2) Note. The subject matter found in this and the indented subclasses ordinarily will not include a frequency or phase modulation receiver by name only (i.e., recited as in a frequency modulation receiver, etc.) followed by specific details of an otherwise classifiable system which is not limited by its function to use in a frequency or phase modulation receiver. However, where the disclosure relates to such a frequency or phase modulation receiver and the receiver is included by name only followed by specifically claimed subject matter which is peculiar to such type a receiver, classification will be herein.

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23,for frequency modulation-type radio repeater systems.
42+,for spaced transmitter and receiver systems of the frequency or phase modulation type.
110+,for frequency or phase modulated transmitters, per se.

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178Telegraphy,   subclasses 66.1+ for frequency shift telegraph receivers.
324Electricity: Measuring and Testing,   subclasses 76.39+ for frequency comparison or testing devices; and subclasses 76.77+ for phase comparison means.
329Demodulators,   subclasses 315+ for a frequency demodulator and subclasses 345+ for a phase demodulator.
332Modulators,   subclasses 117+ and 144+ for frequency or phase modulator, per se.
340Communications: Electrical,   subclasses 13.1 through 13.36for phase and frequency responsive selective systems and subclasses 870.18-870.24 for frequency or phase modulated telemetry systems.
343Communications: Radio Wave Antennas,   subclass 17.5 for frequency or phase modulation radar systems; subclasses 100+ for directional receivers utilizing a frequency modulated input.
358Facsimile and Static Presentation Processing,   subclasses 400+ for facsimile systems which may utilize frequency modulation.
370Multiplex Communications,   subclass 215 for multiplex phase modulation, and subclass 483 for multiplex frequency or angle modulation.
375Pulse or Digital Communications,   subclasses 271+ , 302+, and 322+, for frequency or phase modulated carrier wave pulse or digital communications.
  
[List of Patents for class 455 subclass 206]    206Responsive to one of overlapping signals:
 This subclass is indented under subclass 205.  Subject matter in which the receiver has means by which a desired signal is detected regardless of the pressure of an overlapping signal, whether stronger or weaker.
  
[List of Patents for class 455 subclass 207]    207With plural conversion:
 This subclass is indented under subclass 205.  Subject matter including a plurality of mixing or conversion means.

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102,for transmitters with plural stages of modulation.
314,for receivers in general with wave modifying or conversion systems including plural successive conversion stages.

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332Modulators,   subclasses 119+ and 145 for phase or frequency modulators having plural successive stages of modulation.
  
[List of Patents for class 455 subclass 208]    208With synchronized or controlled local oscillator:
 This subclass is indented under subclass 205.  Subject matter including means whereby the operating frequency of a local oscillator device is maintained in synchronism with a reference frequency, is maintained constant or is varied in accordance with a variation of the frequency of an input signal or means whereby some other operating condition of the local oscillator is controlled.

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196,for signal selection based on frequency (e.g., tuning) means combined with local oscillator tuning means.
255,for automatic frequency control or synchronization systems for receivers in general.
316,for frequency modifying or conversion means combined with plural local oscillator means and provided with frequency stabilization means for at least one local oscillator.
502+,for plural spaced transmitter and receiver systems with synchronization means.

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329Demodulators,   subclasses 323+ and 346 for combining locally generated oscillations with a frequency modulated or phase modulated signal respectively.
331Oscillators,   subclasses 1+ for automatic frequency stabilization of an oscillator or oscillators utilizing phase or frequency sensing means.
  
[List of Patents for class 455 subclass 209]    209Plural local oscillators or mixers:
 This subclass is indented under subclass 208.  Subject matter where there is more than one local oscillator or mixer in the receiver.
  
[List of Patents for class 455 subclass 210]    210With carrier amplitude modulation elimination (e.g., specified limiter):
 This subclass is indented under subclass 205.  Subject matter in which the receiver system includes means for the elimination of amplitude modulation components of the input carrier wave signal.
(1) Note. The amplitude modulation component of the input signal wave may arise from any source external to the receiver but most generally arises at the output of the transmitter.

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43,for spaced transmitter and receiver systems of the frequency or phase-modulated type with preemphasis or other predistortion network.

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329Demodulators,   subclasses 318+ for reduction of amplitude variation in a frequency demodulator.
332Modulators,   subclass 18 for modulators with means to remove undesired amplitude modulation.
  
[List of Patents for class 455 subclass 211]    211Combined with other function:
 This subclass is indented under subclass 210.  Subject matter where the tube or circuit which performs the carrier amplitude modulation elimination also performs another function, for example, amplification.
  
[List of Patents for class 455 subclass 212]    212With squelch or other audio output silencing:
 This subclass is indented under subclass 205.  Subject matter wherein the receiver system includes means whereby the receiver is prevented from producing audio-frequency output in the total absence of an input signal or in the absence of a predetermined signal-noise ratio relationship.
(1) Note. The squelch means may be operated by signal energy in the receiver pass band, by noise quieting means, by a combination of the two, or means to prevent undesired variations in the output of the i.f., amplifier from causing a response in the output of the demodulator.
(2) Note. The amplitude limiting means found in this subclass is intended to ensure that the amplitude variations in the modulated wave input to the demodulator are an accurate representation of frequency modulation of the input exclusive of noise or other undesired effects and are not to be confused with the amplitude modulation elimination means found in subclasses 210+.
(3) Note. To complete the field of search for receivers in general utilizing muting or squelching means consult subclass 218.
(4) Note. The squelch means may be operated by an externally generated signal having special modulation characteristics; such systems are classified in subclasses 701-703.
  
[List of Patents for class 455 subclass 213]    213Using specified filter:
 This subclass is indented under subclass 212.  Subject matter in which the squelch or silencing action, or its reverse, is determined by a frequency discriminating means, specifically recited.
(1) Note. The filter means may be high, low, or band pass or reject.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 552+ for miscellaneous unwanted signal suppression utilizing an active filter.
  
[List of Patents for class 455 subclass 214]    214With particular discriminator or detector:
 This subclass is indented under subclass 205.  Subject matter in which the system includes the combination of a frequency or phase-modulation type receiver, which may be broadly claimed, with a specific discriminator or detector means.
(1) Note. For similar subject matter consisting of discriminator means combined with receiver means other than a frequency or phase modulation type receiver the search will be elsewhere in this class, and for frequency or phase discriminator, per se, the search will be elsewhere
(2) Note. For purposes of classification in this subclass the words discriminator and detector are used synonymously and refer to the final means whereby amplitude variations are derived in response to the frequency or phase properties of a signal. The subject matter to be found here is not to be confused with heterodyning or mixing means which is sometimes referred to as the first detector of a receiver. Heterodyning or mixing means will be found in this class (455) subclass 313 and the indented subclasses.

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329Demodulators,   subclasses 315+ for frequency discriminators, and 345+ for phase discriminator. See the definition and search notes in Class 329 for the complete field of search in other related classes and for a statement of the dividing line between the subject matter in that and other related classes.
  
[List of Patents for class 455 subclass 215]    215Superregenerative:
 This subclass is indented under subclass 214.  Subject matter wherein the particular discriminator or detector means is of the superregenerative type.
(1) Note. Superregenerative detector means as such are specifically excluded from the Demodulator Detector Class 329 by the class definition of that class. Such detectors will be found in this class (455) subclasses 323+ below, if the device acts as a conversion means whose output is an intermediate frequency wave to be further acted upon by further states in a receiver circuit, and in subclasses 336+ if the output actually represents the information contained in the modulation signal.
  
[List of Patents for class 455 subclass 216]    216With particular frequency division or multiplication:
 This subclass is indented under subclass 205.  Subject matter including the combination of a frequency or phase-modulation type receiver, which may be broadly claimed, with a specific frequency dividing or multiplying means.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control and subclasses 185+ for stable state circuits which may be utilized as frequency dividers.
331Oscillators,   subclass 51 for frequency dividing, and subclass 53 for frequency multiplying, plural, cascaded oscillators; and subclasses 74+ for systems comprising a free running oscillator combined with particular output coupling network means which may comprise frequency multiplying or dividing means.
377Electrical Pulse Counters, Pulse Dividers, or Shift Registers: Circuits and Systems,   for electrical pulse counters and dividers.
  
[List of Patents for class 455 subclass 217]    217With protection circuit for receiver circuit:
 This subclass is indented under subclass 130.  Subject matter wherein the receiver system is provided with means to protect the entire receiver circuit or elements thereof from damage due to outside electrical influences.
(1) Note. The subject matter found in this subclass will include only devices intended to protect the receiver system from damage from outside sources, such as lightning, overload due to an excessive signal and may consist of means placed in the antenna or collector input circuit, or means incorporated in the receiver circuit itself.

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117+,for transmitters with circuit protective means.
347+,for mechanical protective means.

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330Amplifiers,   subclass 51 for amplifiers combined with automatic disabling switch means.
331Oscillators,   subclass 62 for oscillators with circuit protective means.
343Communications: Radio Wave Antennas,   subclasses 6+ for radar systems which are provided with means, usually a T-R switch for receiver protection; for preventing damage to the receiver due to direct radiation from the transmitter.
361Electricity: Electrical Systems and Devices,   subclasses 112 and 113 for safety and protective systems for electrical devices and equipment, for space discharge means and tuned circuit, respectively.
454Ventilation,   subclass 184 for means for ventilating an enclosed space, such as a radio or a television cabinet.
  
[List of Patents for class 455 subclass 218]    218Squelch:
 This subclass is indented under subclass 130.  Subject matter where the receiver gain is automatically reduced (quieted) in response to a specified characteristic of the input signal.
(1) Note. The specified characteristic is usually a lack of carrier wave or the presence of excessive noise.

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212+,for frequency or phase modulation receivers with squelch.
  
[List of Patents for class 455 subclass 219]    219With automatic gain or volume control:
 This subclass is indented under subclass 218.  Subject matter combined with control of the amplification of the receiver without manual intervention.

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234.1+,for automatic gain or volume control.
  
[List of Patents for class 455 subclass 220]    220Adjustable:
 This subclass is indented under subclass 218.  Subject matter where the level of input signal characteristic at which the squelch will operate is operator variable.
  
[List of Patents for class 455 subclass 221]    221Audio responsive:
 This subclass is indented under subclass 218.  Subject matter where the level of input signal characteristic at which the squelch will operate is operator variable.
  
[List of Patents for class 455 subclass 222]    222Noise controlled:
 This subclass is indented under subclass 218.  Subject matter in which the specified characteristic of the input signal is the presence of an unwanted or spurious signal at the input of the receiver which modifies the wanted signal.

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296+,for noise elimination in general.
  
[List of Patents for class 455 subclass 223]    223Short duration (noise blankers):
 This subclass is indented under subclass 222.  Subject matter where, in response to a noise pulse, the receiver output is squelched for a time period that is relatively short compared to the period of the demodulated signal.
  
[List of Patents for class 455 subclass 224]    224Separate broadband detector channel:
 This subclass is indented under subclass 223.  Subject matter where there is a separate signal path from the receiver input to the detector which has a broader frequency response than a signal path from the receiver input to the squelch circuit.

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303+,for receivers with noise elimination having plural signal paths.
  
[List of Patents for class 455 subclass 225]    225Plural paths:
 This subclass is indented under subclass 218.  Subject matter where the received signal is applied to two or more signal paths.
  
[List of Patents for class 455 subclass 226.1]    226.1Measuring or testing of receiver:
 This subclass is indented under subclass 130.  Subject matter comprising means which, in use, determines qualitatively or quantitatively, a receiver characteristic.
(1) Note. The receiver may not be operative as to communication during test, and the receiver is usually a block and claimed at least nominally.

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250Radiant Energy,   subclass 250 for measuring the wavelength or frequency of radio and microwave.
331Oscillators,   appropriate subclasses for specific elements (e.g., noise generator), with no more than means for coupling to a receiver.
343Communications: Radio Wave Antennas,   subclass 703 for measuring of a signal with an antenna and a nominal receiver or with quantitative means.
  
[List of Patents for class 455 subclass 226.2]    226.2Signal strength:
 This subclass is indented under subclass 226.1.  Subject matter including a means for measuring a signal strength level.

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324Electricity: Measuring, and Testing,   subclasses 76+ for measuring, testing, or sensing electricity, per se.
  
[List of Patents for class 455 subclass 226.3]    226.3Signal-to-noise ratio:
 This subclass is indented under subclass 226.1.  Subject matter including a means for determining a signal-to-noise ratio.
  
[List of Patents for class 455 subclass 226.4]    226.4With meter or indicator:
 This subclass is indented under subclass 226.1.  Subject matter including a means for displaying to a human observer information concerning the receiver characteristics being measured.
  
[List of Patents for class 455 subclass 227]    227Responsive to an input signal of particular predetermined frequency:
 This subclass is indented under subclass 130.  Subject matter wherein the receiver is permanently adjusted in such a manner as to have a response to signals having a carrier wave of a predetermined frequency or a carrier signal having a predetermined identifying modulation frequency superimposed thereon.
(1) Note. The subject matter found in this subclass is restricted to receivers responsive to a particular preselected input activating signal of a predetermined frequency or other preselected characteristic only.

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26+,for unauthorized use prevention systems whereby only a particular receiver means is enabled to receive a message transmitted from the transmitter.
140,for a plurality of receivers selectively activated.
229,for receivers with alarm or alerting means.
352+,for remotely controlled receivers.

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307Electrical Transmission or Interconnection Systems,   subclass 129 for frequency responsive switching systems.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 1+ for miscellaneous discriminating circuits and particularly subclasses 39+ for frequency discriminating.
333Wave Transmission Lines and Networks,   subclasses 165 through 212for wave filters, per se, comprised of passive elements.
340Communications: Electrical,   subclasses 7.2 through 7.63for selective paging devices, subclasses 13.1-13.36 for frequency responsive remote control signal devices, and subclasses 539.1-539.32 for automatic alarm systems operated via radio link.
343Communications: Radio Wave Antennas,   subclasses 5+ for object detection systems responsive to returned signals; and subclasses 113+ for direction finding receiver systems responsive to a particular input signal.
346Recorders,   subclass 37 for recording systems with control means of the radio receiver type.
361Electricity: Electrical Systems and Devices,   subclasses 182+ for electric control circuits for relays which are frequency responsive.
375Pulse or Digital Communications,   subclasses 316+ for pulse receivers which may be selectively responsive.
380Cryptography,   appropriate subclasses for cryptographic prevention of signal unauthorized use.
  
[List of Patents for class 455 subclass 228]    228Responsive to specified modulation (e.g., call alarm, conelrad):
 This subclass is indented under subclass 227.  Subject matter including means for indicating a predetermined modulation in the carrier.
(1) Note. Systems with a two-state indicator such as an alarm light off or on or with a filter passbanding a warning tone, are classified here only if combined with an analog carrier wave communication receiver.
(2) Note. Selective systems responsive to a predetermined signal(s) are classified in Class 340, subclasses 147+.

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340Communications: Electrical,   subclasses 539.1 through 539.32for an alarm system with a radio link.
343Communications: Radio Wave Antennas,   subclasses 100+ for directive receivers.
  
[List of Patents for class 455 subclass 229]    229Responsive to carrier absence or presence:
 This subclass is indented under subclass 227.  Subject matter including means for indicating the absence or presence of the carrier in a receiver.
(1) Note. The responsive means may energize an alarm or two-state device.
(2) Note. Systems for indicating carrier level or strength, or for indicating tuning, are classified in subclass 154.
  
[List of Patents for class 455 subclass 230]    230Local control of receiver operation:
 This subclass is indented under subclass 130.  Subject matter including provision for controlling an operating characteristic of the receiver.
(1) Note. The control may be automatic or manual.
(2) Note. Remote control is excluded from this subclass and will be found in subclasses 352+.
  
[List of Patents for class 455 subclass 231]    231Applied at or for specific intervals or periods of time:
 This subclass is indented under subclass 230.  Subject matter including means whereby the control voltage or signal is applied to the receiver at or for specific intervals or periods of time.
(1) Note. The time interval determining means may include electrical time constant circuits, mechanical means, or electron tube means.

SEE OR SEARCH CLASS:

178Telegraphy,   appropriate subclasses for telegraph receivers combined with control means which may be activated at or for particular time intervals.
200Electricity: Circuit Makers and Breakers,   subclasses 35+ for clock actuated switching means.
307Electrical Transmission or Interconnection Systems,   subclasses 141+ for time delay or retarded switching systems.
318Electricity: Motive Power Systems,   subclasses 443+ for means for periodically, repetitiously, or successively activating a motor control means; and subclasses 445+ for automatic or time delay means in a motor control circuit.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 261+ for miscellaneous output waveform production delay and subclasses 518+ for miscellaneous control circuits.
330Amplifiers,   subclass 9 for amplifiers with periodic switching of the input.
334Tuners,   appropriate subclass for clock controlled tuners, per se.
340Communications: Electrical,   subclasses 309.16 through 309.9for timer controlled systems.
343Communications: Radio Wave Antennas,   subclass 113 for direction finding receivers which may have time controlling means.
368Horology: Time Measuring Systems or Devices,   subclasses 89+ for timepiece time interval measurement, per se.
369Dynamic Information Storage or Retrieval,   subclasses 6+ for combined radio and phonograph systems.
370Multiplex Communications,   appropriate subclasses for time division multiplex.
  
[List of Patents for class 455 subclass 232.1]    232.1Gain control:
 This subclass is indented under subclass 230.  Subject matter wherein the operating characteristic is the ratio of the output of an amplifier to its input.
(1) Note. The subject matter included in this and the indented subclasses will include patents relating to either signal gain or signal volume control combined with a receiver system since the terms are used more or less synonymously in the art.

SEE OR SEARCH THIS CLASS, SUBCLASS:

136,and 138, for plural separate receivers with output control means.
206+,for automatic volume control means.
210,for frequency or phase modulation type receivers with output limiting means.
254,for means to maintain specified signals-to-noise ratio (i.e., sensitivity control).

SEE OR SEARCH CLASS:

375Pulse or Digital Communications,   subclass 345 for pulse receivers with automatic amplitude control.
  
[List of Patents for class 455 subclass 233.1]    233.1With diverse control (tone, etc.):
 This subclass is indented under subclass 232.1.  Subject matter including significantly claimed details of gain control means combined with other control means (e.g., tone control).
(1) Note. To complete the field of search in this class for subject matter found in this subclass, further search must be made in the appropriate subclass relating to the particular other control mean. For example, wherein the other control means comprises frequency control, further search subclasses 255+, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:

177.1,for receivers with manual selection means combined with other control means.
256,for receivers with frequency control means combined with other control means.
  
[List of Patents for class 455 subclass 234.1]    234.1Automatic:
 This subclass is indented under subclass 232.1.  Subject matter comprising means for automatically controlling the gain as a function of some characteristic of the received carrier wave (e.g., signal amplitude) or some other conditions.
(1) Note. For information as to the field of search for similar subject matter outside this class, see "SEARCH CLASS", under subclass 232.

SEE OR SEARCH THIS CLASS, SUBCLASS:

205,for frequency or phase-type receivers with automatic gain or volume control.

SEE OR SEARCH CLASS:

375Pulse or Digital Communications,   subclass 345 for pulse-type receivers with automatic gain or volume control.
  
[List of Patents for class 455 subclass 234.2]    234.2Processor controlled:
 This subclass is indented under subclass 234.1.  Subject matter wherein the automatic means includes a programmable controller.
  
[List of Patents for class 455 subclass 235.1]    235.1Forward acting:
 This subclass is indented under subclass 234.1.  Subject matter wherein the automatic gain acts on a stage subsequent to a detector stage.
  
[List of Patents for class 455 subclass 236.1]    236.1Variable conversion efficiency (variable oscillator amplitude, etc.):
 This subclass is indented under subclass 234.1.  Subject matter wherein the receiver is a super heterodyne receiver with a frequency converter wherein the ratio of the output to the input of the frequency converter is variable.

SEE OR SEARCH THIS CLASS, SUBCLASS:

311,for noise or the interference elimination means in converter circuit.
313+,for frequency modifiers or converters.
  
[List of Patents for class 455 subclass 237.1]    237.1Responsive to locally injected pilot:
 This subclass is indented under subclass 234.1.  Subject matter wherein the other condition is responsive to a changing amplitude of a local reference signal via the amplifier stages.
  
[List of Patents for class 455 subclass 238.1]    238.1Responsive to vehicle speed:
 This subclass is indented under subclass 234.1.  Subject matter wherein the other condition is responsive to the speed of a vehicle.

SEE OR SEARCH THIS CLASS, SUBCLASS:

297,for noise or other interference elimination in a vehicle receiver.
345+,for receivers combined with vehicles.
  
[List of Patents for class 455 subclass 239.1]    239.1Nonlinear automatic gain control:
 This subclass is indented under subclass 234.1.  Subject matter wherein the output of the amplifier does not rise or fall in direct proportion to the input.
  
[List of Patents for class 455 subclass 240.1]    240.1Variable automatic gain control loop gain:
 This subclass is indented under subclass 239.1.  Subject matter wherein the ratio of the output to the input of the amplifier is controlled by an automatic gain control circuit containing a closed signal path (loop) having variable gain.
  
[List of Patents for class 455 subclass 241.1]    241.1Different gain stages:
 This subclass is indented under subclass 239.1.  Subject matter wherein the receiver contains plurality of amplifiers, the gain of each amplifier being different.
  
[List of Patents for class 455 subclass 242.1]    242.1Delayed:
 This subclass is indented under subclass 239.1.  Subject matter including a means to delay the output with respect to the input.
  
[List of Patents for class 455 subclass 242.2]    242.2Different delays for different signal stages or thresholds:
 This subclass is indented under subclass 242.1.  Subject matter wherein the delay means is responsive to the input signal level of the amplifier or to the signal level in another amplifier.
  
[List of Patents for class 455 subclass 243.1]    243.1Radio frequency stage only delayed:
 This subclass is indented under subclass 242.1.  Subject matter wherein only the automatic gain control of the radio frequency stages of the receiver is delayed.
  
[List of Patents for class 455 subclass 244.1]    244.1Dual time constant:
 This subclass is indented under subclass 239.1.  Subject matter having two different periods of time to maximize the time response related to the carrier wave (e.g., fast response for a high carrier frequency and slow response for a low carrier frequency).
  
[List of Patents for class 455 subclass 245.1]    245.1Automatic gain control signal derived from information signal:
 This subclass is indented under subclass 234.1.  Subject matter wherein the gain control is derived from the demodulated (usually the audio) signal.
  
[List of Patents for class 455 subclass 245.2]    245.2Plural stages controlled:
 This subclass is indented under subclass 245.1.  Subject matter wherein the automatic gain control signal controls at least two or more stages.
  
[List of Patents for class 455 subclass 246.1]    246.1Responsive to plural inputs:
 This subclass is indented under subclass 234.1.  Subject matter wherein the gain control signal is responsive to more than one signal characteristic or other condition.
  
[List of Patents for class 455 subclass 247.1]    247.1Separate automatic gain control signals:
 This subclass is indented under subclass 246.1.  Subject matter wherein there are two or more different automatic output signals.
  
[List of Patents for class 455 subclass 248.1]    248.1Constant or controlled input impedance:
 This subclass is indented under subclass 234.1.  Subject matter wherein the automatic gain control means varies or keeps constant the input impedance of the receiver.
  
[List of Patents for class 455 subclass 249.1]    249.1Variable attenuator type:
 This subclass is indented under subclass 234.1.  Subject matter comprising a circuit that absorbs part of the received carrier wave and transmits the remainder with a minimum of distortion or delay, the amount absorbed being variable.
  
[List of Patents for class 455 subclass 250.1]    250.1Automatic gain control to improve strong signal handling:
 This subclass is indented under subclass 234.1.  Subject matter wherein automatic gain control is used to prevent the receiver from becoming overloaded by a strong received signal.
  
[List of Patents for class 455 subclass 251.1]    251.1Plural stages with different levels or bias to each stage (e.g., partial automatic gain control):
 This subclass is indented under subclass 234.1.  Subject matter wherein there are a plurality of stages in the receiver who have their gain automatically controlled by the application to said stages of different bias or gain control signal levels.
  
[List of Patents for class 455 subclass 252.1]    252.1Semiconductor:
 This subclass is indented under subclass 234.1.  Subject matter having at least one semiconductor device (e.g., transistor, integrated circuit, etc.).
  
[List of Patents for class 455 subclass 253.1]    253.1Plural stages controlled with plates, screen grids, or cathodes connected in parallel:
 This subclass is indented under subclass 234.1.  Subject matter wherein the receiver has a plurality of stages which have vacuum tubes which have plates, cathodes, or screen grids connected in parallel to an automatic gain, level, or volume control voltage.
  
[List of Patents for class 455 subclass 253.2]    253.2Plural amplifier stages:
 This subclass is indented under subclass 234.1.  Subject matter including two or more gain stages.
  
[List of Patents for class 455 subclass 254]    254Sensitivity control:
 This subclass is indented under subclass 230.  Subject matter including significant means whereby the input signal to a receiver system is controlled in such a manner as to produce a predetermined specified output signal having a specified signal to noise ratio.

SEE OR SEARCH THIS CLASS, SUBCLASS:

232.1,for gain, level, or volume control systems.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclasses 5+ for radar systems including receivers which may include sensitivity control; and subclasses 100+ for directive systems which may include sensitivity control.
  
[List of Patents for class 455 subclass 255]    255Local oscillator frequency control:
 This subclass is indented under subclass 230.  Subject matter including one or more local oscillators combined with means to adjust the generated frequency thereof or with a control circuit or loop for controlling the oscillator frequency adjusting means in response to deviation of the generated oscillator frequency from a desired frequency or range of frequencies in such direction and amount as to restore the oscillator frequency to the desired frequency or range of frequencies.
(1) Note. The control circuit or loop includes: (a) discriminator means for sensing the deviation of the generated frequency of the oscillator, or oscillators, in direction and amount and for producing control energy proportional to such deviation, and (b) means responsive to the control energy and coupled to frequency adjusting means of the oscillator, or oscillators, to the desired frequency or range of frequencies whereby the intermediate frequency output of a mixer means, to which the output of the oscillator, or oscillators, is applied will remain constant at a given frequency or range of frequencies.

SEE OR SEARCH THIS CLASS, SUBCLASS:

147,for panoramic type receivers with local oscillator control means.
196.1+,for wave selection (i.e., tuning) means combined with local oscillator tuning means.
208+,for phase or frequency modulation type receivers with synchronized or controlled local oscillator means.
226,for measuring, testing, or calibrating apparatus for receivers which may include oscillator control means.
316,for wave or modifying or conversion systems with frequency stabilization means for at least one local oscillator.

SEE OR SEARCH CLASS:

332Modulators,   subclasses 123+ for controlling an average condition of a frequency modulator and subclasses 155+ and 161+ for controlling an average condition of an amplitude modulator.
  
[List of Patents for class 455 subclass 256]    256Combined with other control:
 This subclass is indented under subclass 255.  Subject matter including significantly claimed details of frequency control means (as defined in subclass 255) combined with other control means (e.g., tone control, selectivity control) or other broadly included control means which may be included by the name only (e.g., volume control).
(1) Note. To complete the field of search for subject matter found in further search must be made in subclasses, or classes, relating to other control means. For example, if the other control means comprises selectivity control the further search should be in subclass 266, etc.
  
[List of Patents for class 455 subclass 257]    257Automatic:
 This subclass is indented under subclass 255.  Subject matter wherein the control means consists of a self-acting control circuit or loop whereby the output frequency of the oscillator means or the output of the mixer means is maintained constant at a desired frequency or within a desired frequency range. The control circuit or loop generally includes discriminator means for sensing the deviation of the oscillator output frequency in direction and amount with means for producing a control energy corresponding to the sensed deviation and applying the generated control energy to a controlling means in the oscillator circuit in the proper sense or direction to restore the oscillator output frequency to a desired value.
(1) Note. Systems wherein the frequency deviation of the output of the conversion means (i.e., intermediate frequency) is sensed and a control energy applied in such a direction as to compensate for the deviation are also found here.

SEE OR SEARCH CLASS:

331Oscillators,   subclasses 1+ for similar subject matter relating to oscillator systems of general utility having automatic frequency stabilization means. See Lines With Other Classes and Within That Class, and References to Other Classes, in the class definition of Class 331 and the search notes under subclass 1 of that class.
  
[List of Patents for class 455 subclass 258]    258Utilizing particular local oscillator control:
 This subclass is indented under subclass 257.  Subject matter including automatic frequency control means broadly included with significantly recited details of one or more particular elements within the control circuit whereby the frequency, control of the oscillator is stabilized or adjusted in response to a deviation from the desired frequency.

SEE OR SEARCH CLASS:

331Oscillators,   subclasses 1+ for oscillators in general having automatic frequency stabilization means, particularly subclass 8 for transistorized controls; subclasses 10+ for plural controls; and subclasses 34+ for particular-type frequency control means.
  
[List of Patents for class 455 subclass 259]    259Reference oscillator or source:
 This subclass is indented under subclass 258.  Subject matter wherein the control means comprises a reference oscillator or source.

SEE OR SEARCH CLASS:

331Oscillators,   particularly subclasses 18+ for automatic frequency stabilized oscillators with reference oscillator or source.
  
[List of Patents for class 455 subclass 260]    260Phase lock loop or frequency synthesizer:
 This subclass is indented under subclass 259.  Subject matter having either a closed-loop electronic servomechanism the output of which locks onto or tracks the reference signal or a frequency source of high accuracy whose output frequency, is composed of two components.
  
[List of Patents for class 455 subclass 261]    261Variable reactance (e.g., reactance tube):
 This subclass is indented under subclass 258.  Systems wherein the control means comprises variable reactance means. The variable reactance means may consist of a reactance tube or a solid-state type variable reactance means, e.g., in the oscillator circuit, the reactance of which is a function of applied bias voltage.

SEE OR SEARCH CLASS:

331Oscillators,   subclass 36 for automatic frequency stabilized oscillators with particular frequency control reactance device.
  
[List of Patents for class 455 subclass 262]    262Voltage controlled capacitor:
 This subclass is indented under subclass 261.  Subject matter in which the variable reactance is a device whose capacitance varies in accordance with a control voltage applied to the device.
  
[List of Patents for class 455 subclass 263]    263Discriminator or detector:
 This subclass is indented under subclass 258.  Subject matter wherein the control means comprises a device in which amplitude variations are derived in response to frequency or phase variations.

SEE OR SEARCH CLASS:

329Demodulators,   appropriate subclasses for demodulators, per se.
331Oscillators,   particularly subclasses 3 , 9, 25+, and 32+ for automatic frequency stabilized oscillators with discriminator means.
  
[List of Patents for class 455 subclass 264]    264Voltage control of oscillator:
 This subclass is indented under subclass 258.  Subject matter having an oscillator the frequency of which can be varied by a changing voltage.
  
[List of Patents for class 455 subclass 265]    265With local oscillator synchronization or locking:
 This subclass is indented under subclass 257.  Subject matter including means whereby a predetermined phase or frequency relationship is maintained between the output of at least one local oscillator and a standard or synchronizing source or wherein the frequency of one or both of two oscillating systems which are coupled together are shifted and automatically held in such a relationship that the two frequencies have the ratio of two integral numbers.

SEE OR SEARCH THIS CLASS, SUBCLASS:

208+,for frequency or phase modulation type receivers with synchronized or controlled local oscillator means.
502+,for complete systems comprising plural transmitters and/or receivers with synchronizing means.

SEE OR SEARCH CLASS:

331Oscillators,   for synchronized oscillators; subclasses 18+ for automatic frequency control type; subclass 55 for plural oscillators; subclass 145 for multivibrators; subclass 149 for blocking oscillators; and subclass 172 for oscillators of general utility and having synchronizing means.
375Pulse or Digital Communications,   subclasses 354+ for synchronizing systems which may utilize oscillators of the automatic frequency stabilized type.
  
[List of Patents for class 455 subclass 266]    266Selectivity or bandwidth control:
 This subclass is indented under subclass 230.  Subject matter including significant means for controlling the extent to which the receiver is capable of differentiating between a desired signal and disturbances of the other frequencies or whereby the difference between the limiting frequencies of a band of frequencies over which the receiver is operative may be varied.

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193.1,and 289, for systems comprising the combination of receiver systems with input wave selection means.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 39+ for miscellaneous frequency comparing, selecting, or detecting circuits.
333Wave Transmission Lines and Networks,   subclasses 167+ for passive wave filters which may be of the adjustable bandwidth type, especially subclasses 177+ for transformer coupled type (e.g., intermediate frequency transformers).
334Tuners,   particularly subclass 40 for tuners with sensitivity or "Q" adjustment means.
  
[List of Patents for class 455 subclass 267]    267Tone control:
 This subclass is indented under subclass 230.  Subject matter including significant details of means whereby a part of the frequency range of the low frequency signals in an audio frequency amplifier of a receiver is emphasized or attenuated to produce a desired bass or treble effect thereby obtaining a quality more pleasing to the ear of a listener when the signals are reproduced.
(1) Note. Where the claimed subject matter comprises significant details of some specific control means other than tone control with tone control means claimed broadly, classification will be in the appropriate subclass for such other control means with an official cross-reference in this subclass.

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84Music,   subclass 622 for electronic musical instruments with tone generation and/or control of tone partials.
330Amplifiers,   appropriate subclasses for amplifiers with equalizing or tone control networks.
333Wave Transmission Lines and Networks,   subclasses 28+ for equalizing networks of the passive type including tone controls which vary the signal attenuation characteristics over a range of frequencies.
  
[List of Patents for class 455 subclass 268]    268Fidelity control:
 This subclass is indented under subclass 230.  Subject matter including significant means for controlling the degree to which a signal transmission system, consisting of a receiver system, reproduces at its output the essential characteristics of a signal impressed upon the input.
(1) Note. Systems which involve nothing more than noise elimination or control means will not be found in this subclass but, unless claimed as part of a more comprehensive system, will be classified in subclasses 296+.
(2) Note. For complete information as to the extent of the field of search for similar subject matter in other classes, see "SEARCH CLASS", under subclass 254.

SEE OR SEARCH THIS CLASS, SUBCLASS:

267,for receivers with tone control means.
  
[List of Patents for class 455 subclass 269]    269With wave collector (e.g., antenna):
 This subclass is indented under subclass 130.  Subject matter wherein the receiver includes wave collecting or antenna means combined with the whole or a specific part of a receiver system and wherein the claimed combination does not form a subcombination of a more comprehensive otherwise classifiable systems.
(1) Note. For purposes of classification in this class the word collector is generic to antenna and includes, in addition to antennas, such devices as inductive pickup coils and other devices intended to supply radio frequency or carrier wave energy to the input of a receiver. In this and the indented subclasses the collector system will include the antenna or coil along with the connecting circuitry up to the input terminals of a preselector, radio frequency amplifier or mixer means which forms the first stage of a receiver.
(2) Note. An antenna or collector means as defined in this class will include a physical device in the form of a metallic current conductor, waveguide, or space discharge device in direct engagement with free space and whereby an electromagnetic energy wave or a wave travelling in restricted space.
(3) Note. Nominal recitation of antenna, or of "antenna circuit" plus specifics of an indent below is sufficient to classify herein.
(4) Note. The combination of significant antenna structure and significant radio structure is classified herein. However, where detailed antenna structure is combined with nominally recited radio structure, classification is in Class 343, subclasses 700+. For example, such terms as transmitter, receiver, and signal source are considered nominal recitations of radio structure.

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178Telegraphy,   subclass 43 for space induction telegraphy systems.
191Electricity: Transmission to Vehicles,   for means for transmitting electrical energy between relatively moving parts, one of which may be a movable antenna, and particularly subclass 10 for magnetic induction systems; subclasses 12.2+ where a reel is involved; and subclasses 22+ where a conductor presenting a substantially continuous exposed surface along the path of movement for contact with a collector is involved.
246Railway Switches and Signals,   subclasses 8 , 63, and 194 for inductive signalling systems which may involve inductive coupling devices similar to loop antennas; and subclass 30 for Hertzian wave systems involving antennas. See also the reference to Class 246 under section VIII of the class definition of Class 343.
250Radiant Energy,   subclass 250 for radio and microwave meters which may include an antenna or probe as an element of the combination.
315Electric Lamp and Discharge Devices: Systems,   subclass 34 for the structural combination of an electric discharge device and an antenna integrally united.
318Electricity: Motive Power Systems,   subclass 16 for electric motors controlled by space transmitted electromagnetic wave energy (e.g., by radio) or electrostatic energy.
324Electricity: Measuring and Testing,   appropriate subclass for electrical testing methods and apparatus that may include the use of radio waves, induction fields, or electric fields.
332Modulators,   subclass 174 for absorption type amplitude modulators which may include a directive antenna.
343Communications: Radio Wave Antennas,   subclasses 5+ for radar systems which may include an antenna; subclasses 100+ for directive systems including beacons and direction finding receivers utilizing; and subclasses 700+ for miscellaneous significant antenna systems and structure, particularly subclass 702 for antenna combined with a radio cabinet; subclass 703 for antenna combined with means for measuring the signal received; and subclass 711 for antenna combined with a vehicle. See also the definitions and search notes of subclasses 700+ for the field of search for other apparatus or systems utilizing antennas or means for supporting and or orienting antennas.
348Television,   appropriate subclasses for television systems that may include radio wave antennas.
358Facsimile and Static Presentation Processing,   appropriate subclasses for facsimile systems that may include radio wave antennas.
  
[List of Patents for class 455 subclass 270]    270Power-line or receiver element used as wave collector:
 This subclass is indented under subclass 269.  Subject matter wherein a portion of a power-line, or a specified receiver element, is used as the formal wave collector.
(1) Note. Receiver elements such as the power transformer, an external structure or the speaker leads may be used.

SEE OR SEARCH CLASS:

340Communications: Electrical,   subclasses 12.32 through 12.39for remote control over power line, subclass 288 for signal box-type alarm circuit over power line, and subclasses 538-538.17 for condition responsive indicating over power line.
  
[List of Patents for class 455 subclass 271]    271Suppression of radiation from receiver via wave collector:
 This subclass is indented under subclass 269.  Subject matter wherein a circuit is provided in the coupling, or in the receiver, for the purpose of reducing emission from the collector.
(1) Note. For a structural means (shielding) which may have the same purpose, see subclass 300.
  
[List of Patents for class 455 subclass 272]    272Plural separate collectors:
 This subclass is indented under subclass 269.  Subject matter in which there are two or more separate and distinct collecting means combined with a single receiving system.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclasses 725+ for plural separate diverse type antennas; subclasses 729+ for plural diverse type antennas using the same active element; subclasses 776+ for plural waveguide type antennas; subclass 844 for plural antennas spaced a fractional or full wavelength apart (e.g., diversity); subclass 869 for plural loop antennas; subclass 879 for support means for plural antennas; and subclass 893 for plural antennas in general.
370Multiplex Communications,   appropriate subclasses for systems which may employ plural antenna to receive a plurality of messages or carriers (i.e., multiplex).
  
[List of Patents for class 455 subclass 273]    273With particular output combining:
 This subclass is indented under subclass 272.  Subject matter including significant details relating to particular combining means in the output circuit of the antennas or collectors and in which the single input to the receiver is a resultant function of the combination in some manner the various outputs of a plurality of separate collectors or antennas.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclasses 725+ for plural antennas with impedance matching or coupling networks.
  
[List of Patents for class 455 subclass 274]    274Loop or coil antenna:
 This subclass is indented under subclass 273.  Subject matter where at least one of the collectors consists of one or more loops of wire.
(1) Note. The loops of wire may be wound around a core of magnetic material or a form made of insulating material or may be self-supporting.
  
[List of Patents for class 455 subclass 275]    275With frequency changing or selecting in the output path of one or more collectors:
 This subclass is indented under subclass 272.  Subject matter including specific details relating to frequency changing or fixed frequency selecting in the output path of at least one or more of the plurality of separate antennas or collectors and not comprising an integral part of the receiver proper.

SEE OR SEARCH THIS CLASS, SUBCLASS:

193.1,for signal selection based on frequency with antenna circuit tuning.
289,for coupling varying, regulating, or control.
313+,for frequency modifying or conversion.
  
[List of Patents for class 455 subclass 276.1]    276.1With phase shifting, correcting, or regulating in the output path of one or more collectors:
 This subclass is indented under subclass 272.  Subject matter including specific details relating to phase shifting and/or regulating means in the output path of at least one or more of the plurality of separate antennas or collectors.

SEE OR SEARCH CLASS:

323Electricity: Power Supply or Regulation Systems,   subclasses 212 through 219for electrical systems (i.e., power frequency systems) wherein a single electrical source circuit is coupled to a single electrical lead circuit and including means whereby the phase angle between the current or voltage of either or both of said circuits is automatically controlled.
324Electricity: Measuring and Testing,   subclasses 76.77+ for systems for measuring, testing, or sensing electricity, per se, by phase comparison.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 141+ for miscellaneous synchronizing circuits and subclasses 231+ for miscellaneous phase shift circuits.
333Wave Transmission Lines and Networks,   subclasses 100+ for branched circuits that may include passive type equalizing or phase delay networks; subclass 18 for automatically controlled equalizer or phase control networks of the passive type; and subclasses 138+ for passive type wave equalizers, per se.
  
[List of Patents for class 455 subclass 277.1]    277.1Selectively or alternately connected to receiver:
 This subclass is indented under subclass 272.  Subject matter including a means to connect any one of the plurality of antennas to the single receiving system.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclass 725 for plural diverse type antenna structures which may be selectively employed; subclass 742 for a plurality of high frequency loop type antennas; subclass 777 for a plurality of waveguide antennas with switching means; and appropriate other subclasses for particular types of plural antennas which may be selectively utilized.
  
[List of Patents for class 455 subclass 277.2]    277.2By signal quality (e.g., noise):
 This subclass is indented under subclass 277.1.  Subject matter wherein the means is responsive to a signal noise.
  
[List of Patents for class 455 subclass 278.1]    278.1Combined with noise or interference elimination:
 This subclass is indented under subclass 272.  Subject matter including noise or interference elimination combined with or in the output circuit of at least one of the plurality collectors.
(1) Note. The claimed noise or interference elimination found in this subclass will be combined with or in the output path of at least one of a plurality of claimed antenna, collector device, or antenna circuit and generally consist of static or other noise elimination but may comprise correction for fading or other interfering signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:

283,for noise reduction or elimination in the output circuit of a single claimed antenna or collector means.
296,for noise or interference reduction or elimination means within or comprising an integral part of the receiver circuitry or structure.

SEE OR SEARCH CLASS:

343Communications: Radio Wave Antennas,   subclasses 850+ for antenna structure with coupling network or impedance in the lead-in which may include noise or static suppression means, particularly subclass 851 for such networks with radiation suppressor.
  
[List of Patents for class 455 subclass 279.1]    279.1Plural antenna currents entering single transformer:
 This subclass is indented under subclass 278.1.  Subject matter wherein one transformer is used in coupling the collectors to the receiver.
  
[List of Patents for class 455 subclass 280]    280With coupling to a stage of the receiver:
 This subclass is indented under subclass 269.  Subject matter including wave collector and a receiver stage coupled by a specified coupling means.
(1) Note. For purposes of classification in this class a tuned circuit connected between the grid and cathode of a tube and variably tunable will be considered as a preselector stage and not a part of the collector coupling circuit. Subject matter relating to preselector circuit means will be found in this class (455) subclass 193.1.
(2) Note. The word detector as defined in this and the indented subclasses will refer to a demodulator means and is not to be confused with mixer means sometimes referred to in the patent literature as a first detector with the demodulator being referred to as a second detector. In this and other subclasses in this class the word detector when used will always denote the demodulator or second detector means. Note that prior to the advent of the heterodyne type of receiver the antenna was usually connected directly to a radio frequency amplifier-detector means or detector means along with the output connected directly to some utilization means such as headphones.
(3) Note. Class 329, Demodulators, contains some demodulators combined with other elements such as an amplifier or speaker. The search notes to that class under the general class definition list combinations considered as classifiable in Class 329 and elsewhere. It will be noted that this Class is specifically mentioned as the proper place for "radio receivers generally including combinations of antennas and detectors or demodulators" and superheterodyne detectors (i.e., mixers).
(4) Note. As an example of the difference between subject matter to be found in this and indented subclasses and that to be found in this class under signal selection based on frequency, subclasses 150.1+ let it be assumed (a) that the system claimed or disclosed consists of a collector circuit including the primary of an inductive transformer, one terminal of which is connected to ground and the other in a closed loop including the collector, or (b) a tunable circuit including the secondary of the input transformer and an amplifier having the tunable circuit connected between the grid and cathode thereof. For classification purposes in this subclass the collector loop circuit including the primary winding of the transformer (a) will be considered as a particular coupling circuit (i.e., transformer) between the collector and amplifier and will be found in subclass 292. The tunable circuit in the input of the tube means which also includes a winding of the transformer (i.e., secondary) (b) will be considered as a wave selecting means in combination with an amplifier means and will be found in subclasses 150+.

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129+,for transmitters with coupled antenna.
214+,for frequency or phase modulation receivers with particular discriminator.
313+,for receiver including particular wave conversion or mixer means.
337,for receiver including particular discriminator means.
341+,for receiver including particular amplifier means.

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178Telegraphy,   subclass 2 for miscellaneous telegraphy systems which may comprise an antenna combined with detector or amplifier means.
315Electric Lamp and Discharge Devices: Systems,   subclass 34 for electric lamp and discharge lead devices having an antenna combined therewith as a unitary structure and not otherwise classifiable.
329Demodulators,   appropriate subclasses for demodulator systems, per se.
330Amplifiers,   appropriate subclasses for amplifiers, per se.
331Oscillators,   subclasses 37+ for beat frequency oscillator, per se.
332Modulators,   appropriate subclasses for modulators, per se.
343Communications: Radio Wave Antennas,   appropriate subclasses for radar, receivers consisting of an antenna combined with detector or other means. Search also subclasses 850+ for antenna structure combined with a coupling network or impedance in the leading. The leading is defined in the definition of Class 343 as being, "a conductive means for conveying the signal energy between the active antenna and the signal source or receiver.
  
[List of Patents for class 455 subclass 281]    281Having distributed parameters:
 This subclass is indented under subclass 280.  Subject matter wherein the coupling means is a system whose constants, such as a resistance, inductance or capacitance, cannot be considered as concentrated at any one point in space.

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333Wave Transmission Lines and Networks,   appropriate subclasses.
361Electricity: Electrical Systems and Devices,   subclasses 297+ for printed circuits structure.
  
[List of Patents for class 455 subclass 282]    282Transmission line:
 This subclass is indented under subclass 281.  Subject matter wherein the coupling means comprises a transmission line.
(1) Note. The transmission line may be a lumped element artificial line, coaxial, shielded, or other configuration such as a Lecher wire.

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333Wave Transmission Lines and Networks,   subclasses 24+ for coupling networks consisting of passive elements and having long line characteristics; subclasses 236+ for long lines in general; and subclasses 245+ for long line elements and components.
343Communications: Radio Wave Antennas,   subclass 905 for antenna structure combined with long line elements.
  
[List of Patents for class 455 subclass 283]    283Undesired signal or noise control (e.g., antistatic):
 This subclass is indented under subclass 280.  Subject matter in which the coupling means acts to reduce signals or noise from the frequency spectrum of the desired signal.
(1) Note. For purposes of classification in this and subsequent subclasses any undesired signal or electrical disturbance within the useful frequency band will be considered to be noise and any unwanted and random noise caused by atmospheric conditions or electric or electrostatic discharges originating from other sources external of and influencing the collector will be considered as static. For systems comprising means, within the receiver circuit, for prevention, reduction, or elimination of noise and/or other interference search will be in this class (455), subclasses 296+ below.

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278.1,for plural antennas for a single receiver with noise or interference suppressing means.
296,for similar systems wherein the collector is not claimed. See (1) Note above.

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174Electricity: Conductors and Insulators,   subclasses 32+ for anti-inductive structures.
307Electrical Transmission or Interconnection Systems,   subclasses 89+ for anti-induction or coupling means for prevention of inductive coupling to other circuits; and subclass 93 for surge, transient, or parasitic current suppression means.
333Wave Transmission Lines and Networks,   subclass 12 for wave transmission line inductive or radiation interference reduction systems.
343Communications: Radio Wave Antennas,   appropriate subclasses for antenna structure combined with impedance means in the leadin which may serve as interference attenuation means, particularly subclass 851 for antenna combined with coupling network having radiation suppressing means.
  
[List of Patents for class 455 subclass 284]    284Balancing or cancelling:
 This subclass is indented under subclass 283.  Subject matter including significant means for producing a balancing or neutralizing current or voltage of opposite phase and equal intensity to that resulting from the unwanted signal whereby the unwanted signal is suppressed at the input to the receiver.
  
[List of Patents for class 455 subclass 285]    285With image frequency suppression:
 This subclass is indented under subclass 283.  Subject matter wherein the coupling includes means whereby an unwanted signal appearing at the collector and whose frequency differs from the received signal by twice the intermediate frequency, is suppressed or eliminated.
(1) Note. For similar structure not tuned specifically to the superheterodyne image frequency refer to subclass 286 in a noise reducing system, and subclass 290 for general wave collector coupling systems using tuned circuits.

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302,for image frequency suppression in general.
  
[List of Patents for class 455 subclass 286]    286Wave filter, coil or wave trap:
 This subclass is indented under subclass 283.  Subject matter including means whereby undesired signals differing in frequency from the desired signal are absorbed and thus prevented from appearing at the input terminals of the receiver.

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193.1,for receivers having tuned antenna coupling means in general.
287,for similar means comprising a shunt or bypass.
307,for receivers in general with filter means for reduction of the effects of noise or other interference.

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333Wave Transmission Lines and Networks,   subclasses 24+ for coupling networks consisting of passive element devices; and subclasses 165-212 for passive element wave filters.
  
[List of Patents for class 455 subclass 287]    287Shunt or bypass:
 This subclass is indented under subclass 283.  Subject matter including means whereby any undesired signal or signals are shunted or bypassed to ground and thus prevented from appearing at the input terminals of the receiver.

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285,and 286, for similar means comprising a resonant circuit or filter in a noise reduction system.
  
[List of Patents for class 455 subclass 288]    288Particular composition (e.g., of cell or element):
 This subclass is indented under subclass 283.  Subject matter wherein the significant noise and/or static reduction or elimination means comprises an element utilizing a material or composition which conducts or varies its impedance selectively so as to attenuate the noise or static energy and permit message of the desired signal without attenuation.

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257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses for specific active solid- state devices which show nonlinear behavior.
  
[List of Patents for class 455 subclass 289]    289With coupling varying, regulating, or control:
 This subclass is indented under subclass 280.  Subject matter wherein the coupling means includes means whereby the reaction of the antenna or collector output circuit upon the receiver input circuit of the receiver is varied, maintained constant, or controlled by design to react over the frequency range in a desired way.
(1) Note. An example of the subject matter to be found in this subclass is an antenna connected to the input of a receiver through a variometer.
(2) Note. The systems to be found here are variable tuned circuits in the antenna or collector-receiver coupling circuits and are not intended to be utilized as preselector or tuning means for the receiver. For wave selecting (i.e., tuning), search this class (455), for subclass 193.1.

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343Communications: Radio Wave Antennas,   subclasses 854 and 861 for adjustable antenna coupling means.
  
[List of Patents for class 455 subclass 290]    290Including passive tuned circuit:
 This subclass is indented under subclass 280.  Subject matter where the coupling is a fixed tuned circuit.
(1) Note. The systems to be found here comprise tuned circuit means in the antenna or collector receiver coupling circuits and are not intended to be utilized as preselector or tuning means for the receiver but often times are utilized to determine the frequency of the signal accepted by the antenna or collector and transmitted to the receiver input terminals. For wave selecting (i.e., tuning) circuits utilized for the determination of the frequency to which a receiver is tuned, search this class (455), subclass 193.

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283+,for receivers using tuned circuits in the antenna coupling for undesired signal or noise control.
289,for receivers with variable tuned circuits in antenna coupling systems.
340,for receivers using variable resonant or tuned circuits in coupling systems.
  
[List of Patents for class 455 subclass 291]    291Using active device (e.g., as preamplifier or reactance):
 This subclass is indented under subclass 280.  Subject matter wherein the coupling means includes an electron tube device, solid state device, transistor, diode, or other active device whereby the magnitude of the high frequency signal applied to the receiver may be maintained constant or other wise influenced.
(1) Note. The coupling means may act merely as a resistive impedance in the coupling circuit, or may act as an amplifier.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   for miscellaneous nonlinear circuits utilizing active devices.
330Amplifiers,   appropriate subclasses for amplifiers.
  
[List of Patents for class 455 subclass 292]    292Transformer or other passive inductance:
 This subclass is indented under subclass 280.  Subject matter wherein the coupling means includes at least the primary winding of a transformer or other inductive means.
(1) Note. For purposes of Classification in this subclass the primary winding of an input transformer, the secondary winding of which, along with a capacitor or other tuning means constitutes the wave selecting or tuning means in the input of a receiver, will be considered to be in the coupling circuit and will be found in subclasses 289 and 290.

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284,285, 286, and 287, (note also) where inductances may be used in noise reducing coupling circuits.
289,where variometers and variable inductances are classified.
290,where tuned circuits using inductances are classified.

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343Communications: Radio Wave Antennas,   subclasses 745+ for antenna structure combined with variable reactance for tuning the antenna; subclasses 749+ for antenna structure combined with lumped reactance for leading the antenna; and subclasses 850+ for antenna structure combined with impedance means in the leadin.
  
[List of Patents for class 455 subclass 293]    293Specified stage (e.g., mixer, amplifier, or demodulator):
 This subclass is indented under subclass 280.  Subject matter wherein the coupling means is connected to at least a named stage of the receiver.
  
[List of Patents for class 455 subclass 294]    294With particular electron tube structure:
 This subclass is indented under subclass 293.  Subject matter in which the stage has an electron or other charged particle space discharge device or devices characterized by special tube construction or electrode arrangement combined with sufficient circuitry to define the assembly as a system such as is excluded from the other subclasses in this class and related other art devices classified elsewhere.
(1) Note. The circuitry means to be found in this subclass consists of the circuitry comprising that associated with the tube itself and is not to be confused with the coupling means between the collector and the tube input found in the subclasses above this class.

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193.1,where there is a tunable circuit between the collector and the tube input.
291,wherein the electron tube constitutes a coupling impedance or amplifier between collector and receiver input.

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313Electric Lamp and Discharge Devices,   appropriate subclasses for all lamp and discharge devices, per se, where significant lamp or discharge device structure only is claimed, combined with means for modifying the temperature of the lamp or discharge device, and with separate casing, jacket, shield, enclosure, or envelope protecting means.
315Electric Lamp and Discharge Devices: Systems,   appropriate subclasses for discharge devices of various types combined with circuitry for controlling the tube and in which no load for the tube is claimed.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   particularly subclasses 598+ for miscellaneous electron tube devices characterized by special tube construction or electrode arrangement combined with sufficient circuitry to control the tube or provide an output from the tube and not otherwise classifiable.
329Demodulators,   appropriate subclasses for various electron tube devices used as demodulators and not combined with sufficient structure as to define a complete receiver.
330Amplifiers,   appropriate subclasses for various electron tube devices used as amplifiers and not forming a part of more comprehensive system classifiable elsewhere.
331Oscillators,   appropriate subclasses for various electron tube devices combined with sufficient circuitry to constitute a free running oscillator system and not forming a subcombination of a more comprehensive system classified elsewhere.
  
[List of Patents for class 455 subclass 295]    295Modulation distortion or cross talk correction or elimination:
 This subclass is indented under subclass 130.  Subject matter including means whereby intermodulation components occurring in a desired modulated carrier wave input signal, due to cross-modulation of the desired carrier by an undesired signal wave, are corrected for or whereby distortions of a desired modulated carrier wave input signal, which are due to causes other than interference external to the receiver system, are corrected for or eliminated.
(1) Note. Some examples of the various sources of distortion are selective fading, attenuation in the transmitting medium, cross-talk, etc.
  
[List of Patents for class 455 subclass 296]    296Noise or interference elimination:
 This subclass is indented under subclass 130.  Subject matter having structure to (a) suppress the influence of extraneous electric or magnetic fields upon receiver circuitry, (b) prevent radiation of undesired electric or magnetic fields from the receiver circuitry, or (c) prevent translation through, or suppress at some point in, the receiver system any undesired modulation components accompanying a desired modulation carrier wave input signal which components are due to electrical disturbances within the useful frequency band or any undesired carrier wave, which may originate at a source external to the receiver wave input or collection means and arrive at the input or collector simultaneously with the desired modulated carrier wave.
(1) Note. The extraneous fields or undesired components may be due to external sources or internally generated noises or disturbances due to microphonica or regenerative effects.

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63.1through 65, for complete systems with noise prevention.
175.1+,for frequency selection (tuning) means combined with muting means.
219,for volume control systems combined with noise squelch means.
278.1+,for plural antennas with noise elimination means connected to a receiver.
283+,for subject matter relating to noise or static reduction or eliminating means within the coupling circuit between a collector (antenna) means and the input terminals of a receiver.
295+,for receivers with signal intermodulation or cross talk correction or elimination means.
298+,for receivers with hum or interaction prevention means in the power or bias supply.
317+,for frequency modifying or conversion systems including means for the prevention of unwanted oscillations.
501+,for complete systems comprising a plurality of transmitters or receivers with noise reduction.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 310+ for transient reduction by limiting or clipping, subclasses 379+ for miscellaneous reduction of gating noise, and subclasses 551+ for miscellaneous unwanted signal suppression.
330Amplifiers,   appropriate subclasses for amplifiers with limiting means.
340Communications: Electrical,   subclass 600 for systems for detecting a signal bearing useful information accompanied by noise.
343Communications: Radio Wave Antennas,   subclasses 5+ for object detection radar systems having noise or interference prevention means; and subclasses 100+ for directive radio wave receivers which may have interference prevention means.
348Television,   subclasses 607+ for noise elimination in television systems.
370Multiplex Communications,   appropriate subclasses for multiplex systems having interference suppression.
375Pulse or Digital Communications,   subclass 285 for complete systems utilizing pulse modulation and having distortion or noise prevention means; and subclasses 346+ for pulse type receivers with interference or noise reduction means.
  
[List of Patents for class 455 subclass 297]    297In vehicle:
 This subclass is indented under subclass 296.  Subject matter wherein the receiver is located in self-propelled movable conveyance.
(1) Note. For purposes of classification in this class, aircraft, land vehicles, and water craft are all considered to be vehicles under the general meaning of the word.

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11.1+,for mobile radio repeater stations.
95,for mobile or portable transmitters.

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343Communications: Radio Wave Antennas,   subclasses 705+ for antennas combined with aircraft; and subclasses 711+ for antennas combined with other vehicle.
  
[List of Patents for class 455 subclass 298]    298Originating in power supply:
 This subclass is indented under subclass 296.  Subject matter where the noise or other interference arises in the receiver power supply.

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343.1through 343.6, for receiver power supplies in general.
  
[List of Patents for class 455 subclass 299]    299Filter or rectification in power supply energized by fluctuating or A. C. source:
 This subclass is indented under subclass 298.  Subject matter having means to smooth or integrate the current or voltage of energization before application thereof to the signal processing components, the energizing circuit also having means to make the voltage or current unidirectional (i.e., D.C.) prior to application to such smoothing or integrating means, if necessary.
  
[List of Patents for class 455 subclass 300]    300By shielding:
 This subclass is indented under subclass 296.  Subject matter wherein the field suppression structure is a field-resistant body interposed between the field source and the region in which the suppression is desired.
(1) Note. The body is generally an enclosure containing the receiver or a portion thereof.
  
[List of Patents for class 455 subclass 301]    301Plural or compartmented shielding structure:
 This subclass is indented under subclass 300.  Subject matter wherein the shielding structure shields plural elements of the receiver by either (a) including plural shielding devices, or (b) including compartments in a single device.
  
[List of Patents for class 455 subclass 302]    302Image frequency suppression:
 This subclass is indented under subclass 296.  Subject matter comprising the combination of frequency modifying or conversion means with significant details of means whereby an unwanted signal appearing at the output of the conversion means, and whose frequency differs from the desired signal by twice the intermediate frequency, is suppressed or eliminated.
  
[List of Patents for class 455 subclass 303]    303Using plural separate signal paths:
 This subclass is indented under subclass 296.  Subject matter comprising means for receiving a modulated carrier input signal wave consisting of a plurality of signal translating channels including at least one main channel, which one channel includes means for selecting a carrier component having a first characteristic type of modulation representing a desired signal as well as a second type of modulation representing undesired signal disturbances, and at least one other auxiliary signal translating channel comprising means for selectively detecting only modulation representing undesired signal disturbances and means responsive to the output of both channels to reduce or cancel the effects of the undesirable signal disturbances.

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375Pulse or Digital Communications,   subclass 349 for a signal receiver with a noise or interference reduction circuit comprising plural signal paths.
  
[List of Patents for class 455 subclass 304]    304Phase shift in at least one path:
 This subclass is indented under subclass 303.  Subject matter wherein at least one of the separate signal paths includes phase shifting or delaying.

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333Wave Transmission Lines and Networks,   subclasses 138+ for passive phase delay networks, per se.
  
[List of Patents for class 455 subclass 305]    305With balancing or neutralizing:
 This subclass is indented under subclass 303.  Subject matter in which the outputs of the plural separate paths are combined in such a manner as to balance out or neutralize the modulation representing the undesired signal disturbances.

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283,for receivers with particular noise or static balancing or neutralizing means coupled between the antenna and receiver.
  
[List of Patents for class 455 subclass 306]    306Filter in at least one path:
 This subclass is indented under subclass 305.  Subject matter where at least one signal path offers comparatively little opposition to certain frequencies or to direct current, while blocking or attenuating other frequencies.
  
[List of Patents for class 455 subclass 307]    307With specific filter structure:
 This subclass is indented under subclass 296.  Subject matter which offers comparatively little opposition to certain frequencies or direct current while blocking or attenuating other frequencies.
  
[List of Patents for class 455 subclass 308]    308With amplitude limiter:
 This subclass is indented under subclass 296.  Subject matter wherein the noise or interference reduction means includes diode or other amplitude limiting means.
  
[List of Patents for class 455 subclass 309]    309In demodulator or low frequency (audio amplifier circuit):
 This subclass is indented under subclass 308.  Subject matter wherein the diode or other amplitude limiting means is a part of or associated with the demodulator or audio frequency circuits of the receiver.

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329Demodulators,   particularly subclasses 321 and 350 for amplitude limiting in a frequency or amplitude demodulator respectively.
  
[List of Patents for class 455 subclass 310]    310Internally generated noise or oscillations:
 This subclass is indented under subclass 296.  Subject matter where the noise or other interference that is eliminated is noise or oscillations which arise from the receiver"s own circuitry (except power supply).

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298+,for elimination of noise arising in the receivers power supply.
  
[List of Patents for class 455 subclass 311]    311In radio frequency amplifier, intermediate frequency amplifier or converter circuit:
 This subclass is indented under subclass 296.  Subject matter in which the noise or interference reduction means forms an integral part of or is associated with the circuitry of the radio frequency amplifier, frequency converter, intermediate frequency amplifiers of the receiver stages or the coupling circuit between any two of the three stages.

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307,for noise or interference reduction means comprising filter means. The filter means may be located anywhere in the system and may consist of either a single filter or a plurality of filters.
  
[List of Patents for class 455 subclass 312]    312In demodulator or low frequency (e.g., audio frequency) amplifier circuit:
 This subclass is indented under subclass 296.  Subject matter wherein the noise or interference reduction means forms an integral part of or is electrically associated with the circuitry of the demodulator or the low frequency (e.g., audio frequency) amplifier stages of the receiver.
  
[List of Patents for class 455 subclass 313]    313Frequency modifying or conversion:
 This subclass is indented under subclass 130.  Subject matter including means whereby a modulated carrier wave signal is changed to another carrier frequency, e.g., an intermediate frequency signal, the frequency of which lies between that of the modulated input signal and the frequency of the lower frequency modulating signal.
(1) Note. In this and the indented subclasses the frequency conversion is usually accomplished by combining a modulated carrier wave input signal with the output of a local oscillator means (i.e., by mixer means).

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196.1+,for variation of local oscillator frequency combined with signal frequency selection.
255+,for local oscillator frequency control.

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307Electrical Transmission or Interconnection Systems,   subclass 424 for nonoptical parametric amplifier frequency converters, per se.
324Electricity: Measuring and Testing,   subclass 76.41 for systems for measuring, testing, or sensing of electricity by heterodyning; and subclass 85 for phase comparison systems utilizing frequency conversion.
327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control.
331Oscillators,   subclasses 37+ for beat frequency oscillators.
332Modulators,   appropriate subclasses for modulators in general.
343Communications: Radio Wave Antennas,   subclasses 6+ for radar receivers which may utilize frequency conversion means; and subclasses 100+ for directional receivers utilizing frequency converters.
348Television,   appropriate subclasses for television systems which may include frequency conversion.
359Optics: Systems and Elements,   subclasses 326+ for optical frequency translators.
370Multiplex Communications,   appropriate subclasses for multiplex systems which may include frequency conversion.
  
[List of Patents for class 455 subclass 314]    314Plural separate successive conversions:
 This subclass is indented under subclass 313.  Subject matter comprising a plurality of separate frequency modifying or conversion means or stages, the modulated input wave being passed through the frequency conversion stages in succession.
  
[List of Patents for class 455 subclass 315]    315With plural separate local oscillators:
 This subclass is indented under subclass 314.  Subject matter including separate local oscillator means combined with at least two or more of the plural separate conversion means.
  
[List of Patents for class 455 subclass 316]    316With frequency stabilization for at least one local oscillator:
 This subclass is indented under subclass 315.  Subject matter including means whereby the output frequency of at least one of the plurality of separate local oscillator means is stabilized.
  
[List of Patents for class 455 subclass 317]    317Unwanted oscillation or radiation prevention:
 This subclass is indented under subclass 313.  Subject matter including frequency modifying or conversion means combined with other means whereby any unwanted or parasitical oscillations originating in the receiver circuitry are eliminated or whereby any oscillations occurring in the receiver circuitry are prevented from being reradiated from the receiving antenna.

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174Electricity: Conductors and Insulators,   for electric shielding structures in general.
307Electrical Transmission or Interconnection Systems,   subclass 89 for anti-induction systems in general.
329Demodulators,   appropriate subclasses for demodulators having radiation reducing means.
343Communications: Radio Wave Antennas,   subclasses 5+ for radar receivers with reradiation prevention means; and subclasses 100+ for directive systems which may have radiation control.
  
[List of Patents for class 455 subclass 318]    318With specified local oscillator structure or coupling:
 This subclass is indented under subclass 313.  Subject matter including significant details of either (a) at least one source of unmodulated signal for frequency conversion, or (b) circuitry connecting a source of unmodulated signal to a frequency conversion device.

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196.1+,for signal selection based on frequency including variation of local oscillator frequency.
255+,for control of local oscillator frequency.
  
[List of Patents for class 455 subclass 319]    319With particular coupling:
 This subclass is indented under subclass 318.  Subject matter including significant details of circuitry whereby the output of the local oscillator means is coupled to the frequency modifying or conversion means.

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338,for subject matter relating to particular coupling means between stages of a receiver system.
  
[List of Patents for class 455 subclass 320]    320Lumped impedance:
 This subclass is indented under subclass 319.  Systems where substantially all impedance in the coupling means is concentrated in components, as distinguished from impedance due to stray or distributed effects.
  
[List of Patents for class 455 subclass 321]    321In a single envelope or with common active element (e.g., autodyne):
 This subclass is indented under subclass 318.  Subject matter wherein the frequency modifying or conversion means and the local oscillator means are enclosed in a single envelope.
(1) Note. The combination of means may comprise: (a) a single triode or diode type tube structure with external circuitry whereby a local signal is generated and superposed on a modulated signal input, (b) two or more assemblies of electrodes to which the local signal and the modulated input signal are applied, (c) a single assembly of electrodes to some of which the local signal is applied and to others of which the modulated wave input is applied. One example of the subject matter to be found here is the autodyne system in which the same electron tube device constitutes both an oscillator and a mixer (1st detector).

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 591 for miscellaneous circuits where an electron tube performs plural functions.
329Demodulators,   subclasses 323+ , 346 and 358+ for diverse types of demodulators using locally generated oscillations.
331Oscillators,   subclass 58 for oscillators performing plural functions simultaneously.
  
[List of Patents for class 455 subclass 322]    322Plural common electrode:
 This subclass is indented under subclass 321.  Subject matter wherein the conversion means and local oscillator means are combined in a single electron tube having a plurality of separate control grids.
  
[List of Patents for class 455 subclass 323]    323Particular frequency conversion structure or circuitry:
 This subclass is indented under subclass 313.  Subject matter including significant details of the frequency modifying or conversion means.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclasses 113+ for miscellaneous frequency conversion or control.
  
[List of Patents for class 455 subclass 324]    324Homodyne (e.g., zero beat or synchrodyne reception):
 This subclass is indented under subclass 323.  Subject matter comprising frequency conversion or modifying means and combined with means whereby a local signal wave of the same frequency as the incoming modulated wave is injected therein (i.e., zero beat).

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329Demodulators,   subclasses 323+ , 346 and 358+ use of synchronized oscillations locally generated in a frequency, phase, or amplitude demodulator, respectively.
  
[List of Patents for class 455 subclass 325]    325Including distributed electrical parameter structure:
 This subclass is indented under subclass 323.  Systems comprising frequency conversion means including significant structural elements of such dimensions that their distributed constants (e.g., inductance, capacitance, resistance, or conductance) must be taken into account.
(1) Note. The distributed inductance or capacity may be either in the conversion device or associated circuitry.
(2) Note. The subject matter found here generally consists of systems where the combination of a detecting element and structure having distributed electrical parameters and which system is restricted by disclosure or claims to mixers or converters. Where the combination is claimed generically with general detection use suggested in the specification, or with both mixer and detector use suggested in the specification, classification is in Class 329, subclasses 160+ or other appropriate subclasses.

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329Demodulators,   subclasses 322 and 354 for distributed parameter structure in a frequency or amplitude demodulator, respectively.
330Amplifiers,   subclass 43 for travelling wave tube amplifiers; subclass 44 for electron beam tube amplifiers; subclass 47 for magnetron amplifiers; and subclass 49 for electron vacuum tube amplifiers with distributed electrical parameter elements.
331Oscillators,   appropriate subclasses for oscillators with distributed parameter resonator, particularly subclass 42 for beat frequency oscillators with cavity mixer.
332Modulators,   subclasses 129+ for distributed parameter structure in a frequency modulator and subclasses 163+ for distributed parameter structure in an amplitude modulator.
333Wave Transmission Lines and Networks,   appropriate subclasses for passive wave transmission networks of the distributed parameter type.
  
[List of Patents for class 455 subclass 326]    326With balanced mixer:
 This subclass is indented under subclass 325.  Systems including two or more identical frequency conversion devices arranged in conjugate relationship about a neutral or grounded point, the output of the system comprising a linear combination of the separate input signals.
(1) Note. The subject matter to be found here will include systems in which input signals are applied to the input of the mixer or conversion devices 180 apart, with the output signal being derived in additive relationship (i.e., push-pull).

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332Modulators,   subclasses 154 and 180 for push-pull circuits in an amplitude modulator and subclass 172 for an amplitude modulator utilizing a bridge circuit.
  
[List of Patents for class 455 subclass 327]    327Stripline:
 This subclass is indented under subclass 326.  Systems where the distributed electrical parameter structure is in the form of a thin, narrow rectangular strip adjacent to a wide ground-plane conductor or between two wide ground-plane conductors.
  
[List of Patents for class 455 subclass 328]    328Hollow waveguide:
 This subclass is indented under subclass 326.  Subject matter in which the distributed electrical parameter structure is a transmission line comprising a hollow conducting tube.
  
[List of Patents for class 455 subclass 329]    329Electron beam tube:
 This subclass is indented under subclass 325.  Subject matter wherein the frequency conversion means comprises electron beam tube means.

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332Modulators,   appropriate subclasses for a pulse, frequency, phase or amplitude modulator utilizing electron beam tubes.
  
[List of Patents for class 455 subclass 330]    330With nonlinear impedance (e.g., diode):
 This subclass is indented under subclass 325.  Subject matter having a device connected to the distributed electrical parameter structure, said device having an output that does not rise or fall in direction proportion to the input.
  
[List of Patents for class 455 subclass 331]    331Crystal or electron tube diode:
 This subclass is indented under subclass 323.  Systems and in which the frequency conversion means consists of crystal or other type (e.g., electron tube) diode devices of the two terminal or electrode type. The diodes may be of passive rectifier type or active such as a negative resistance (e.g., tunnel or Esaki diode).

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326+,for plural diode mixers forming a balanced mixer combined with distributed parameter structure.
330+,for a diode mixer combined with nonlinear structure.
333,for frequency converters of the semiconductor active element type having three or more terminals.

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329Demodulators,   subclasses 203+ for demodulating devices consisting of diode or two electrode devices.
332Modulators,   subclasses 139+ for piezoelectric devices in a frequency modulator, subclass 172 for an amplitude modulator having a bridge which may include a nonlinear device, and subclasses 176+ for a nonlinear device in an amplitude modulator.
  
[List of Patents for class 455 subclass 332]    332Push-pull:
 This subclass is indented under subclass 323.  Systems wherein the frequency conversion means includes two paths for either the modulated input carrier wave or locally generated signal wave, or both, which have a common output, the two paths being connected electrically in parallel with respect to the input and output of the paths the voltages in the two paths being 180 of phase with respect to each other.

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329Demodulators,   appropriate subclasses for demodulators having balanced input.
330Amplifiers,   subclass 118 for push-pull amplifiers.
332Modulators,   subclasses 154 and 180 for push-pull circuits in an amplitude modulator.
  
[List of Patents for class 455 subclass 333]    333Transistor or integrated circuit:
 This subclass is indented under subclass 323.  Systems wherein the frequency conversion means comprises an active element, three or more terminal device or devices constructed of a semiconductor material having a specific resistance, for example, of the order of that of germanium, silicon, selenium, etc. (e.g., transistor).
(1) Note. For specific types of receivers which may include semiconductor devices, see the pertinent subclass relating to the particular special type receiver in this class.

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257Active Solid-State Devices (e.g., Transistors, Solid-State Diodes),   appropriate subclasses integrated circuit structure with active solid-state devices, subclasses 446 and 499+ for integrated circuit devices with electrically isolated components, in general, and other appropriate subclasses for specific type devices in integrated circuits.
329Demodulators,   appropriate subclasses for demodulators using a discrete semiconductor device.
330Amplifiers,   subclasses 250+ for amplifiers with transistors.
331Oscillators,   subclasses 108+ for oscillators utilizing transistor type active element.
348Television,   subclasses 659+ for natural color television with mixing.
  
[List of Patents for class 455 subclass 334]    334With particular receiver circuit:
 This subclass is indented under subclass 130.  Subject matter comprising subcombinations peculiarly adapted for use in a receiver system, and consisting of an electron tube or other active elements combined with particular electric circuit means in either the input or output thereof.
(1) Note. This subclass and its indented subclasses provide for subject matter peculiar to and forming subcombinations of receiver apparatus which are not sufficiently comprehensively claimed for classification above in this class, but which claim sufficient significant structure to exclude the subject matter claimed from art classified elsewhere. See Search Notes under subclass 130.
  
[List of Patents for class 455 subclass 335]    335Plural diverse function tube or stage (performs plural functions alternately or concurrently):
 This subclass is indented under subclass 334.  Subject matter including at least one electron space discharge device which is provided with circuit means for performing at least two independent functions either simultaneously or selectively.
  
[List of Patents for class 455 subclass 336]    336Superregenerative detector or discriminator:
 This subclass is indented under subclass 334.  Subject matter comprising systems of the type where, in the detector, oscillations are alternately allowed to build up and are quenched at a frequency which is high compared with the modulation frequency.
(1) Note. The quench voltage may be supplied either by the detector itself or it may be supplied separately by a separate quenching oscillator.
(2) Note. The superregenerative devices found here are very similar to the detector or demodulator systems found in Class 329. However, the superregenerative systems have been excluded from that class since they are more in the nature of a combination of amplifier plus a first detector (i.e., mixer) in which the input comprises a modulated wave and in which the output voltage representing the modulating signal. Therefor, even though the devices to be found here are often claimed as detectors, they are excluded from the detector Class 329 and, since this is the generic class for modulated carrier wave communication systems, they are to be classified here as wave frequency conversion devices. See section III under the class definition of Class 329 for a further understanding of the line of demarcation between the two as to this subject matter.
  
[List of Patents for class 455 subclass 337]    337Discriminator or demodulator:
 This subclass is indented under subclass 334.  Systems including discriminator or demodulator means associated with sufficient significant circuitry so as to be limited to use in a receiver system.
(1) Note. Some examples of subject matter to be found in this subclass are detector means in combination with antenna means and frequency discriminator means deriving an output other than the modulation signal, etc.

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327Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   particularly subclasses 2+ for miscellaneous phase discrimination, subclasses 39+ for miscellaneous frequency discrimination, and subclasses 334+ for a miscellaneous circuit providing an output which is a nonlinear function of an input.
329Demodulators,   subclasses 315+ , 345+ and 347+ for frequency, phase or amplitude demodulators, respectively. See also the Class Definition of Class 329 for additional relevant areas of search.
  
[List of Patents for class 455 subclass 338]    338Coupling or decoupling between stages:
 This subclass is indented under subclass 334.  Systems including means whereby two or more stages or systems are electrically associated in such a manner that electrical effects in one produce similar effects in the other or networks are used to prevent interaction or coupling between two electric circuits.

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280+,for receivers with particular coupling means between antenna and input circuit.
319+,for local oscillator with particular coupling.

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330Amplifiers,   appropriate subclasses for amplifiers with coupling or decoupling means.