This is the generic class for electrical oscillators.

LINES WITH OTHER CLASSES AND WITHIN THIS CLASS
ELECTRICAL OSCILLATORS OR WAVE GENERATORS OR PRODUCERS CLASSIFIED ELSEWHERE
See Classes in References to Other Classes, below.
OSCILLATOR COMBINED WITH OTHER APPARATUS OR SYSTEMS
See References to Other Classes, below.

REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:
84, Music, subclasses 671-722 for electric oscillator tone generation systems combined with, or restricted to use with, means to convert the generated tone waves into musical sounds. (Oscillator Combined With Other Apparatus Or Systems.)
123, Internal-Combustion Engines, subclass 148 for significant internal combustion engine structure combined with high tension ignition system, which system may utilize an electric oscillator. (Oscillator Combined With Other Apparatus Or Systems.)
178, Telegraphy, appropriate subclasses, for telegraph apparatus and systems that may employ electrical oscillators; see particularly subclass 43 for space induction systems, subclasses 66.1+ for alternating, sine or similar wave current telegraph systems. (Oscillator Combined With Other Apparatus Or Systems.)
200, Electricity: Circuit Makers and Breakers, subclass 19.01 for the structure of circuit makers and breakers designed to be periodically closed and opened; subclass 136.3 for time-controlled or continuously driven thermal switch.. (Electrical Oscillators or Wave Generators or Producers.)
204, Chemistry: Electrical and Wave Energy, appropriate subclasses for processes and apparatus for producing chemical changes through the agency of electrical wave energy; see
particularly subclasses 155+, 157.15+ and 164+ for the processes, and subclasses 193+ for the corresponding apparatus which may utilize electrical wave energy generators or oscillators. (Oscillator Combined With Other Apparatus Or Systems.)
219, Electric Heating, appropriate subclasses, for electrical heating systems or apparatus that may employ electrical oscillators as elements thereof; subclasses 600+ for inductive heating, subclasses 678+ for microwave heating, and subclasses 764+ for capacitive dielectric heating, (Oscillator Combined With Other Apparatus Or Systems.)
246, Railway Switches and Signals, appropriate subclasses, for railway switching and signaling systems; see particularly subclasses 7+ for train dispatching telegraphy and telephony systems, and subclass 30 for Hertzian wave controlled automatic block signal systems, which systems may employ electrical oscillators. (Oscillator Combined With Other Apparatus Or Systems.)
290, Prime-Mover Dynamo Plants, appropriate subclasses, for prime mover driven dynamo systems, wherein the prime mover is other than an electric motor and wherein the dynamo may be an alternating current generator. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
307, Electrical Transmission of Interconnection Systems, subclasses 106+ for class appropriate waveform or wave shape determinative or pulse producing systems (usually of the delay line type) to produce periodic pulses of predetermined wave shape in the output of the network; subclass 132 provides for free-running electromagnetic circuit maker and breaker-type pulse producers. (Electrical Oscillators or Wave Generators or Producers.)
310, Electrical Generator or Motor Structure, appropriate subclasses, for the structure of alternating current generators for converting mechanical energy into electrical energy; subclasses 300+ provides for nondynamoelectric generators (or motors) while subclasses 10+ provides for dynamoelectric machines, subclasses 40+ provides for rotary machines, indented subclass 159 provides for alternating current generators and indented subclasses 169+, in particular, provides for high frequency inductor generators of the variable reluctance type (e.g., Alexanderson alternator). (Electrical Oscillators or Wave Generators or Producers)
315, Electric Lamp and Discharge Devices: Systems, appropriate subclasses, for oscillator systems similar to those classified in this class (331), but wherein no means for deriving a useful output from the system is claimed. See particularly subclasses 3+ for cathode-ray tube circuits including a cathode-ray tube combined with circuit element structure, indented subclasses 3.5+ provides for traveling wave tubes, and indented subclasses 4+ provides for cathode
ray tubes including distributed parameter resonant devices (e.g., cavity resonators); subclasses 39+ provides for discharge devices in general with distributed parameter elements (e.g., wave guides, coaxial lines, which devices usually are resonators); subclasses 227+ provides for gaseous space discharge device systems with capacitor in the supply circuit, many of these systems being self-sustaining oscillators. (Electrical Oscillators or Wave Generators or Producers)
315, Electric Lamp and Discharge Devices: Systems, appropriate subclasses, provides for systems for supplying electrical energy to cathode-ray tubes, electric lamp, diode or gaseous space discharge devices, which systems may be self-oscillatory or wherein the source of supply for the devices may be an electrical oscillator; in particular, subclasses 364+ provides for cathode-ray tube deflecting systems which may utilize an electrical oscillator as a sweep or deflection source, subclass 97 provides for pulsating or A.C. supply for the cathode or heater of plural load device systems and subclass 105 provides for pulsating or A.C. supply for the cathode or heater of a single load device, subclasses 137+ provides for polyphase A.C. supply, subclasses 160+ provides for plural power supplies which may be pulsating or A.C., and subclasses 246+ provides for pulsating or A.C. supply systems in general.
318, Electricity: Motive Power Systems, subclass 130 for reciprocating motor systems wherein the energizing winding circuit of the motor is supplied by an electrical oscillator, and subclass 341 for electric motor control systems wherein the motor armature or primary circuit is supplied by an adjustable frequency or impulse generator or oscillator to control or vary the motor speed. (Oscillator Combined With Other Apparatus Or Systems.)
322, Electricity: Single Generator Systems, appropriate subclasses, for apparatus for converting nonelectric energy directly into electrical energy, which may be alternating current. Except for subclass 2, which provides for nonmagnetic type generator systems (e.g., thermoelectric, photoelectric, piezoelectric, electrostatic generators, etc.), and subclass 3, which provides for reciprocating or oscillating type generators, the remaining subclasses comprise mainly patents directed to rotating dynamoelectric machine generator systems. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
323, Electricity: Power Supply or Regulation Systems, particularly subclass 282 and 351 for intermittently operated final control devices.
324, Electricity: Measuring and Testing, appropriate subclasses, for electrical measuring and testing systems and apparatus which may employ electrical oscillators. For example, subclasses 307+ provides for nuclear induction testing systems utilizing adjustable frequency oscillators to
determine nuclear resonance characteristics of material under test. Also, electrical oscillators may be employed in the following testing and measuring subclasses of Class 324; subclass 56 for piezoelectric crystal testing, subclasses 57+ for impedance and admittance measuring systems, subclasses 76.41+ for heterodyne type frequency measuring systems, subclass 85 for phase comparison systems utilizing frequency conversion, and subclass 118 for electricity measuring systems utilizing modulator-demodulator means. (Oscillator Combined With Other Apparatus Or Systems.)
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclasses 291+ for miscellaneous clock or pulse waveform generation which is not free running. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
329, Demodulators, subclass 302, 306+, 323+, 346, and 358+ for diverse types of demodulator with oscillators. (Oscillator Combined With Other Apparatus Or Systems.)
330, Amplifiers, subclass 10 for linear active element amplifiers of the modulator-demodulator type utilizing an oscillator. (Oscillator Combined With Other Apparatus Or Systems.)
332, Modulators, appropriate subclasses, for electrical oscillators provided with means for varying some characteristic of the generated wave (e.g., amplitude, frequency or phase of a sine wave or pulse repetition rate, position, amplitude, width or slope of a repetitious pulse) in accordance with an intelligence which continually varies in an arbitrary manner. (Oscillator Combined With Other Apparatus Or Systems.)
333, Wave Transmission Lines and Networks, subclass 19 for electric wave differentiating or integrating systems of the passive type; subclass 20 for passive type electric wave shaping networks, and subclasses 219+ for resonators, per se, of the distributed parameter type. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
334, Tuners, appropriate subclasses for tuned networks for use in wave energy apparatus and comprising inductance and capacitance elements in circuit arrangement to form a resonant circuit and in which structure is provided for adjusting one or both of these elements for changing the mean resonant frequency of the circuit.
335, Electricity: Magnetically Operated Switches, Magnets, and Electromagnets, subclasses 87+ for the structure of electromagnetically operated switches of the periodic type. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
337, Electricity: Electrothermally or Thermally Actuated
Switches, subclass 51, 92+ and 301+ for particular types of thermally controlled periodically operated switches. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
340, Communications: Electrical, appropriate subclasses, for electric signaling systems that may employ electrical oscillators; for example, subclasses 203+ provides for oscillators of the pulse modulated or modulating type in a telemetering system; similarly, subclasses 207+ provides for phase or frequency modulated oscillators, subclass 209 provides for amplitude modulated oscillators in a telemetering system, and subclasses 345+ provides for code transmitters which may employ oscillators; and subclasses 825.69 and 825.72 for a control signal used for control purposes. (Oscillator Combined With Other Apparatus Or Systems.)
343, Communications: Radio Wave Antennas, appropriate subclasses, for electrical apparatus or systems directed to the generation, control and radiation or reception of wave energy propagated through free space, which apparatus or systems may employ electrical oscillators; for example, subclasses 5+ provides for reflected or returned wave systems (object detection, radar), subclasses 100+ provides for directive systems. (Oscillator Combined With Other Apparatus Or Systems.)
348, Television, subclasses 536+ and 735 for television systems that may include electrical oscillators. (Oscillator Combined With Other Apparatus Or Systems.)
361, Electricity: Electrical Systems and Devices, subclass 203, for relay systems using an electrical oscillator (Oscillator Combined With Other Apparatus Or Systems.)
361, Electricity: Electrical Systems and Devices, subclasses 268+ for the structure of so-called spark, induction or ignition coils having integral vibratory circuit interrupters, usually in the primary winding circuit and indented subclasses 270+ wherein a capacitor is included. (Electrical Oscillators or Wave Generators or Producers.)
361, Electricity: Electrical Systems and Devices, appropriate subclasses for systems or apparatus that may employ electrical oscillators; particularly, subclass 203 which provides for the combination of an oscillator and electromagnet load and electrical oscillator controlled relay systems. (Oscillator Combined With Other Apparatus Or Systems.)
363, Electric Power Conversion Systems, appropriate subclasses for wave generating or producing systems analogous to those classified in Class 331. Some of the systems for converting direct current to alternating current (e.g., derectifiers, inverters) in Class 363 are indistinguishable from the oscillators in Class 331. The distinction appears
to be one of degree, that is, the inverters classified in Class 363 usually are designed to convert direct current power to alternating current power at commercial power frequency (e.g., 25, 50, or 60 cycles per second). See subclasses 1+ for combined conversion systems, subclasses 9+ for phase and frequency conversion, and subclasses 15+ and 34+ for plural current conversion systems (e.g., D.C.-A.C.-D.C., and A.C.-D.C.-A.C.); subclasses 13+ for current conversion systems (rectification, derectification), subclasses 102+ for dynamoelectric machine converters, subclasses 111+ for electronic tube converters, subclasses 123+ for semiconductor-type converters, subclass 140 for impedance-type converters, subclasses 106+ for circuit interrupter-type converters, and subclasses 157+ for frequency converting systems wherein input alternating current of one frequency is converted into output alternating current without intermediate conversion to direct current. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere)
363, Electric Power Conversion Systems, subclasses 1+ for cascaded or combined diverse conversion, subclasses 13+ for current conversion systems, subclasses 148+ for phase conversion, and subclasses 157+ for frequency conversion systems. (Oscillator Combined With Other Apparatus Or Systems.)
370, Multiplex Communications, appropriate subclasses for oscillators used with multiplexing.
373, Industrial Electric Heating Furnaces, appropriate subclasses, for electric furnaces that may employ an oscillator for supplying or controlling the electric current for the furnaces, see particularly subclasses 138+ for induction furnaces that may utilize an oscillator to supply the furnace charge melting inductor. (Oscillator Combined With Other Apparatus Or Systems.)
375, Pulse or Digital Communications, subclasses 354+ for pulse communications synchronization. (Oscillator Combined With Other Apparatus Or Systems.)
455, Telecommunications, subclasses 91+ for transmitters using electrical oscillators; subclasses 130+ for receivers using electrical oscillators; subclasses 145+ for local oscillators in panoramic receivers; subclass 196 for local oscillator tuning in radio receivers; subclasses 208+ for local oscillator control in frequency modulation receivers; subclasses 255+ for local oscillator control in radio receiver automatic frequency control; and subclasses 313+ for local oscillators insuperhetrodyne receivers. (Oscillator Combined With Other Apparatus Or Systems.)
505, Superconductor Technology: Apparatus, Material, Process, subclasses 150+ for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting devices; and particularly subclass 204 for oscillators or subclass 180
for masers made with high temperature superconducting material. (Electrical Oscillators or Wave Generators or Producers Classified Elsewhere, above.)
505, Superconductor Technology: Apparatus, Material, Process, subclasses 150+ for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting systems that may contain oscillators; particularly subclass 204 for oscillators, or subclass 180 for masers made with high temperature superconducting material. (Oscillator Combined With Other Apparatus Or Systems.)
607, Surgery: Light, Thermal, and Electrical Application, subclasses 72+ for oscillator systems combined with or forming a part of a therapeutic device. (Oscillator Combined With Other Apparatus Or Systems.)

GLOSSARY:
ACTIVE ELEMENT
A control device for exerting a control on a source of energy proportional to an applied control signal. A conventional triode, having cathode, control grid on anode, connected as a conventional amplifier, is an example of an active network, a control potential applied to the grid causing a flow of anode current, supplied by the anode biasing source, proportional to the magnitude of the control potential.
AMPLITUDE STABILIZATION
The correction for, prevention of, or compensation for an undesired change in amplitude of the generated waves of the oscillator from a desired value.
AUTOMATIC FREQUENCY STABILIZATION
The restoration of the generated frequency of the oscillator to a desired value by sensing the deviation in frequency, in direction and amount, from the desired value and instituting a corrective action proportional to sensed deviation to adjust the frequency determining element of the oscillator in such direction and amount so as to return the oscillator frequency to the desired value.
BEAM TUBE
An active element comprising a source of charged particles, means for concentrating the particles into a directed beam, means for exerting a control on the beam (e.g., beam accelerating electrode, control grid, deflecting means, slow wave structure, buncher type resonator, reflector electrode, etc.) and means for deriving output energy from the controlled beam.
BEAT FREQUENCY
The resulting difference (or sum) frequency wave, among other waves, produced when two waves of different frequencies are combined in a nonlinear device.
DISTRIBUTED PARAMETER RESONATOR
A resonator of the distributed network type, the capacitance, inductance and resistance of which cannot be isolated into separate lumped capacitors, inductors or resistors and wherein the time factor of propagation of wave energy in the network is appreciable.
ELECTRICAL NOISE OR RANDOM WAVE GENERATOR
A wave generator system wherein the frequency determining element consists of a material medium including electrically charged, chargeable or ionizable particles, the application of electrical energy to the medium by the driving means causing random translatory motion of the charged or ionizable particles resulting in the generation of an infinite number of waves of different frequencies which are fortuitously related, having no definite phase relationship, period, amplitude or shape.
ELECTROMECHANICAL RESONATOR
A resonator comprising an electrically driven material body wherein the mass and compliance parameters of the body determine the mechanical period of vibration of the body and wherein the driving electrical circuit for the body exhibits electrical resonance characteristics which are determined by the mechanical period of vibration of the body.
FREE RUNNING OSCILLATOR
An oscillator wherein the driving system continuously supplies the losses of the frequency determining means so as to produce sustained oscillations.
FREQUENCY ADJUSTING MEANS
Means for setting or controlling the generated frequency of the oscillator by varying a frequency determining element of the oscillator.
FREQUENCY DETERMINING ELEMENT
A passive network or device of the resonant or time constant type, which network or device forms the element of the oscillator which sets or determines the frequency or periodicity of the generated oscillations.
FREQUENCY STABILIZATION
The correction for, prevention of, or compensation for an undesired drift or change in the frequency of the generated waves of the oscillator from a desired value.
GASEOUS SPACE DISCHARGE DEVICE
A space discharge device having at least two electrodes in a gaseous or vapor medium, conduction between the electrodes taking place by ionization of the medium.
HARMONIC OR SINE WAVE OSCILLATOR
A free running oscillator for generating sinusoidal or nearly sinusoidal waves. They usually utilize a resonator of the lumped LC or the distributed parameter type as the frequency determining element.
HETERODYNE FREQUENCY
Beat frequency (which see).
KLYSTRON
A beam tube including at least two apertured cavity resonators, the beam of charged particles passing through the apertures of the resonators in succession, and a collector electrode being provided to intercept the beam after passing through the resonators. The first resonator causes bunching of the particles passing therethrough, the bunched particles then travel in a field-free region where further bunching occurs and then the bunched particles enter the second resonator giving up their energy to excite it into oscillations.
LC RESONATOR
A resonant circuit comprising separate inductance and capacitance elements, i.e., lumped inductor and capacitor elements.
MAGNETICALLY CONTROLLED SPACE DISCHARGE DEVICE
An active element comprising means for producing a space discharge of charged particles and having further means for subjecting the space discharge to the direct control of a magnetic field and an electric field.
MAGNETRON
A magnetically controlled space discharge device comprising a linear cathode, an anode, usually cylindrical, coaxial therewith, the magnetic field being parallel to longitudinal axis of the cathode, while the electric field is transverse thereto.
MOLECULAR OR PARTICLE RESONANT OSCILLATOR
An oscillator wherein the frequency determining element consists of a material medium comprising particles, molecules or atoms, the application of electrical energy by the driving
means to the medium setting the particles, molecules or atoms into a state of vibration or oscillation, the vibration or oscillation being that of the particle, molecule or atom itself and not the vibration or oscillation caused by the translational motion of the particle, molecule or atom as a whole.
MOLECULAR RESONATOR
A resonator comprising a material medium and wherein the vibration or oscillation of the molecules of the medium determines the resonant frequency of the resonator. The vibration or oscillation is of the molecule itself and not that due to the translational motion of the molecule as a whole. See, also, above, the definition of a molecular or particle resonant oscillator.
NEGATIVE RESISTANCE OR NEGATIVE TRANSCONDUCTANCE DEVICE
An active element of the two terminal type having a volt-ampere characteristic with negative slope over the range of voltages or currents wherein it is operative, that is, an increase in voltage results in a decrease in current, or vice versa.
OSCILLATOR
A system for initiating and maintaining oscillations whose frequency or period is fixed or determined by the physical parameters of the system. The fundamental elements required by an oscillator system are: (1) a frequency or period determining element, such as a resonator or timing means, (2) a driving system for the frequency or period determining element, and (3) means for deriving a useful output from the oscillator system. This class is restricted to oscillators for generating electrical oscillations or waves and specifically excludes alternating current generators of the mechanically driven dynamo-electric machine type.
RC OR RL FREQUENCY DETERMINING NETWORK
A network of the nonresonant type comprising either resistive and capacitive or resistive and inductive components. The network, by way of example, may be employed: (1) as a frequency determining phase shift network in a sine wave oscillator of the phase shift type, (2) as a frequency determining bridge network in sine wave bridge oscillators, such as the Wien bridge type of the double-T type or (3) as a time constant network in a relaxation oscillator to determine the period of the generated relaxation oscillations.
REFLEX KLYSTRON
A klystron utilizing only a single apertured cavity resonator through which the beam of charged particles passes in one direction, a repeller electrode being provided to repel or redirect the beam after passage through the resonator back
through the resonator in the other direction and in proper phase to reinforce the oscillations set up in the resonator.
RELAXATION OSCILLATOR
A free running oscillator for generating decidedly non sinusoidal waves. They usually utilize a time constant network of the RC or RL type as the frequency determining element.
RESONATOR OR RESONANT CIRCUIT
A frequency determining means comprised of substantially pure reactances of opposite signs (i.e., mass and compliance in a mechanical resonator or inductive and capacitive reactance in an electrical resonator) wherein the phenomenon of resonance (i.e., when the positive and negative reactances are equal) is relied upon to determine the frequency of the generated waves.
RETARDING FIELD TUBE
A tube having at least three electrodes, i.e., a source of electrons (cathode), control electrode (grid) and anode or plate electrode, the control electrode being biased positively with respect to the other electrodes. The electrode bias potentials are so chosen that the electrons attracted from the cathode by the positive grid pass through the grid and are slowed down by the repelling effect of the less positive (or negative) anode field and are returned back to or through the grid. This phenomenon is repeated again and again so that a cloud of electrons are caused to sweep back and forth through the grip, giving up energy to the grid at a frequency which is a function of the transit time of the cloud of electrons. The Barkhausen Kurz, Gill-Morrell and the reflex klystron are examples of oscillators utilizing a retarding field tube.
SEMICONDUCTOR ACTIVE ELEMENT
A solid state active element comprised of a solid material having a conductivity intermediate that of a good insulator and a good conductor.
SHOCK EXCITED RESONATOR OSCILLATOR
An oscillator of the nonself-sustaining type wherein the driving system applies an electrical impulse to the frequency determining element (i.e., resonator), which element is then permitted to oscillate freely at its natural frequency.
SOLID STATE ACTIVE ELEMENT
A two-terminal or fourterminal active element of electrically conductive, semi-conductive, ferromagnetic or ferroelectric material in the solid state. Examples are: The Hall effect plate, semi-conductor (transistor), magnetic type and
dielectric type amplifiers or negative resistance devices.
SPACE DISCHARGE DEVICE
A device comprising at least two spaced electrodes and wherein conduction by charged particles, e.g., electrons, or ions, takes place between the electrodes.
STABILIZATION
The maintenance of a desired condition or state of the oscillator which condition or state may be subject to change.
TRANSISTOR
A semi-conductive active element having at least three electrodes so arranged that the application of electrical energy to one electrode controls the flow of current between two other electrodes.
TRANSIT TIME OSCILLATOR
An oscillator system wherein the time of flight or transit angle of charged particles between electrodes of a space discharge device is an appreciable part of the cycle of the generated oscillations, the energy derived from the moving particles being continuously supplied to the frequency determining network of the oscillator in proper phase to sustain oscillations. Transit time effects are utilized in magnetron, beam tube and retarding field type oscillators.
TUBE
An active element of the space discharge device type. See: active element; space discharge device.

This subclass is indented under the class definition. Subject matter wherein the oscillator has means to adjust its generated frequency and is also provided with a control circuit or loop for controlling the oscillator frequency adjusting means in response to deviation of the generated frequency of the oscillator 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. The control circuit or loop includes: (1) discriminator means for sensing the deviation of the generated frequency of the oscillator in direction and amount and for producing control energy proportional to such
deviation, and (2) means responsive to the control energy and coupled to frequency adjusting means of the oscillator to vary the frequency adjusting means in such direction and amount as to restore the generated frequency of the oscillator to the desired frequency or range of frequencies.
(1) Note. The automatic frequency stabilizing systems defined above are to be distinguished from the frequency stabilizing systems classified lower in the schedule (see the search notes below) by the fact that the A.F.S. systems rely on sensing a drift in frequency of the generated oscillations and asserting a corrective control to adjust a frequency determining element of the oscillator in the proper sense to bring it back on frequency, whereas the frequency stabilizing systems classified elsewhere do not sense a drift of frequency and retune the oscillator as a function of such drift, but rely on adding means to the oscillator system to correct or compensate, or to prevent, changes in oscillator circuit parameters that tend to cause an undesired change in oscillator frequency. Such means may, for example, compensate for the affects of changes in humidity, temperature, current load impedance, tube impedance, electrode bias potential, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:
41 for beat frequency oscillators with frequency stabilizing means. See also, (1) Note, above.
88 for magnetron type oscillators with frequency stabilizing means. See, also, (1) Note, above.
subclasses 175+ for oscillators in general with frequency stabilizing means. See, also (1) Note, above.

SEE OR SEARCH CLASS:
322, Electricity: Single Generator Systems, subclass 32 for dynamoelectric generator systems with frequency responsive devices or networks for automatically maintaining the frequency of the generated wave constant.
329, Demodulators, subclasses 315+ for frequency demodulators and subclasses 345+ for phase demodulators.
332, Modulators, subclasses 123+ for average condition control in frequency modulator distortion prevention and subclasses 155+ and 159+ for average condition control in an amplitude modulator.
334, Tuners, subclass 13 for a tuner having a saturable core element combined with means to automatically center the frequency of the circuit; subclass 16 for a tuner having a reactance tuning means combined with automatic frequency centering means, and subclasses 26+ for tuners having an
electromagnetic operator combined with automatic frequency centering means.
348, Television, subclasses 536+ for synchronizing systems which may utilize oscillators of the automatic frequency stabilized type and subclass 735 for television tuners which may utilize oscillators of the automatic frequency stabilized type.
375, Pulse or Digital Communications, subclasses 354+ for synchronizing systems which may use oscillators of the automatic frequency stabilized type.
455, Telecommunications, subclasses 91+ for radio transmitters using oscillators of the automatic frequency stabilized type; and subclasses 130+ for receivers using oscillators of the automatic frequency stabilized type.

This subclass is indented under subclass 1. Subject matter wherein the generated frequency of two or more oscillators is automatically stabilized. The oscillators may have A.F.S. loops individual to each oscillator or a single A.F.S. loop may control two or more oscillators, or any combination of A.F.S. loops may be employed, provided the generated frequency of two or more oscillators is automatically stabilized.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 46+ for plural oscillator systems in general.

This subclass is indented under subclass 1. Subject matter wherein the frequency discriminator or sensing means is of the molecular or atomic resonance type, comprising a medium, which may be solid, liquid or gaseous, the frequency selective properties of which are due to the vibration or oscillation of the individual molecule or atom itself and are not due to the translational motion of the molecule or atom as a whole.

SEE OR SEARCH THIS CLASS, SUBCLASS:
9 for A.F.S. systems utilizing a distributed parameter type
discriminator.
subclasses 25+ for A.F.S. systems utilizing a signal or phase comparing type discriminator having at least two inputs for the signals (of the controlled oscillator and reference source) to be compared.
subclasses 32+ for A.F.S. systems having a single input type discriminator.
78 for electrical noise or random wave generators wherein the translatory motions of charged or excited particles or molecules are utilized to generate oscillations.
94.1 for oscillators of the molecular or particle resonant type (e.g., maser) wherein a molecular or particle resonant solid, liquid or gas comprises the active element of the oscillator.

SEE OR SEARCH CLASS:
250, Radiant Energy, subclass 251 for devices for producing and propagating a unidirectional stream of neutral molecules or atoms through a vacuum, usually at thermal velocity and including means to excite the molecules or atoms at a resonant frequency.

This subclass is indented under subclass 1. Subject matter wherein means are provided, in addition to the A.F.S. loop, for varying the oscillator frequency through a range of frequencies. The systems classified herein are chiefly directed to means for restoring A.F.S. control wherein such control is lost due to the fact that the oscillator frequency for some reason, such as during "warm-up" or some other disturbance, lies outside the "capture" range of the frequency discriminator, the sweep range of frequencies includes the "capture" range of the discriminator and serves to bring the oscillator frequency within the "capture" range and thereby render the A.F.S. effective.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 23+ for oscillators wherein low frequency modulation of the generated oscillations is utilized for A.F.S., signals representative of the frequency modulated
oscillations being compared with signals of the modulating source.
106 for oscillator systems of the periodic amplitude and frequency varying type.
178 for oscillators in general provided with cyclic frequency sweeping means.

This subclass is indented under subclass 1. Subject matter wherein the oscillator provided with A.F.S. is of the magnetic and electric field controlled space discharge device type.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 86+ for magnetron type oscillators in general, particularly subclass 88, for such oscillators provided with frequency stabilization means of the nonautomatic type.

This subclass is indented under subclass 1. Subject matter wherein the oscillator provided with A.F.S. is of the beam tube type utilizing hollow resonator electron bunching or electron bunching and catching means for determining the generated frequency of the oscillator. Such oscillators are generally designated as klystron oscillators.

SEE OR SEARCH THIS CLASS, SUBCLASS:
83 for multi-cavity type klystron oscillators.
84 for reflex type klystron oscillators.

This subclass is indented under subclass 6. Subject matter wherein the oscillator is provided with two or more oscillator frequency controls as part of the A.F.S. system. For example, the A.F.S. system for a reflex klystron
oscillator may (1) control a motor to tune the cavity for coarse tuning and at the same time (2) supply a bias voltage to the reflector electrode for fine tuning of the oscillator.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 10+ for single oscillators provided with two or more A.F.S. controls.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. circuit of the oscillator includes semiconductor means, such as transistors.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 107+ for oscillators wherein the active element is of the solid state type and indented subclasses 108+ wherein the active element is of the transistor type.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. control circuit of the oscillator is provided with a frequency sensing means of the distributed parameter type (e.g., cavity resonator).

SEE OR SEARCH THIS CLASS, SUBCLASS:
3 for A.F.S. systems utilizing a molecular resonance type discriminator.
subclasses 25+ for A.F.S. systems wherein the discriminator is of the signal or phase comparing type having at least two inputs for the signals (of the controlled oscillator and reference source) to be compared.
subclasses 32+ for A.F.S. systems having a single input type discriminator.

This subclass is indented under subclass 1. Subject matter wherein oscillator is provided with two or more A.F.S. means, each having a different effect in tuning the oscillator. For example, one A.F.S. means may provide a coarse tuning control and another A.F.S. means may effect a fine tuning control of the oscillator.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural oscillators involving plural A.F.S. control loops.
7 for klystron oscillators provided with two or more oscillator frequency controls as part of the A.F.S. systems.

This subclass is indented under subclass 10. Subject matter wherein the oscillator system is provided with two or more comparators or discriminators, each of which may be associated with a separate A.F.S. control. By way of examples (1) one discriminator may have a broad band frequency response characteristic and another discriminator may have a narrow band frequency response characteristic or (2) one discriminator may be of the frequency sensitive type, while another discriminator may be of the phase sensitive type.

This subclass is indented under subclass 11. Subject matter wherein at least two comparators are so arranged that the outputs of the controlled oscillator and a reference oscillator are directly compared in one comparator and the output of the controlled oscillator is phase-shifted and then compared with the reference oscillator in a second comparator, the outputs of the comparators then being combined in a control circuit to effect tuning of the controlled oscillator.

This subclass is indented under subclass 10. Subject matter wherein at least one of the A.F.S. controls includes an electric motor for electromechanically adjusting a tuning reactance of the oscillator. Usually the motor control is utilized for coarse tuning while another A.F.S. control of the electronic type (e.g., including a reactance tube) is utilized for fine tuning of the oscillator.

SEE OR SEARCH THIS CLASS, SUBCLASS:
24 for oscillators wherein low frequency modulation of the generated oscillations is utilized for A.F.S. and wherein the signal comparator is of the electric motor type.
29 for oscillators wherein an electromechanical signal comparator is utilized in the A.F.S. loop.
35 for A.F.S. oscillators with electromechanically controlled oscillator frequency adjusting means.

This subclass is indented under subclass 1. Subject matter wherein means are provided to open and close the A.F.S. loop of the oscillator periodically. By way of example, a periodically actuated switch may connect the input of the comparator in the A.F.S. loop of an oscillator alternately to the oscillator output and the reference oscillator output.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. loop circuit of the oscillator is provided with means to limit the amplitude, or to maintain the amplitude constant, or to correct or otherwise compensate for undesired changes in amplitude of a control signal in the loop circuit, or to disable the A.F.S. loop if the amplitude of the control signal (e.g., reference oscillator signal) is below a predetermined level (e.g., the level wherein noise signals may adversely affect the oscillator A.F.S. and thereby cause the generated frequency to be shifted outside its proper range).

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40 for beat frequency oscillators provided with amplitude adjustment or control means.
109 for transistor oscillators provided with amplitude stabilization or control means.
subclasses 182+ for oscillators in general with amplitude control or stabilization.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. controlled oscillator includes means for setting the frequency of the generated oscillations to any selected frequency within a predetermined frequency range, means being provided to interrupt or otherwise deactivate the A.F.S. control loop of the controlled oscillator while changing the generated frequency from one value to another so as to prevent the A.F.S. loop from tending to hold the oscillator frequency to its previously set value, that is, the A.F.S. tends to drag.

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455, Telecommunications, subclasses 255+ for similar A.F.S. systems utilized in radio receivers.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. loop of the oscillator is provided with means to modify or control the error voltage so as to compensate or correct for undesired changes in the error voltage brought about by some deficiency in the oscillator system, such as a drift in reference frequency, hunting due to instability around the A.F.S. loop, undesired shift in phase of side band frequencies, and so forth.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. circuit of the controlled oscillator includes a source of constant frequency, which source serves
as a frequency standard, means being provided for comparing the frequency of the oscillations generated by the controlled oscillator with the standard frequency, the frequency comparison means producing an electrical control or error signal which is a measure of the deviation, in direction and amount, of the controlled oscillator frequency from the standard frequency, the control or error signal being applied to the frequency adjustment means of the controlled oscillator in such a manner as to reduce the frequency difference between the generated oscillations of the controlled oscillator and the oscillations of the constant frequency source to a minimum.

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329, Demodulators, subclasses 323+ for a frequency demodulator using an oscillator and subclass 346 for a phase demodulator using an oscillator.

This subclass is indented under subclass 18. Subject matter wherein the reference source is a spectrum generator producing a plurality of waves of different frequencies, which waves are simultaneously fed to the comparator or discriminator of the A.F.S. circuit of the controlled oscillator means being provided wherein the generated waves of the controlled oscillator may be selectively locked-in to the desired frequency of the spectrum.
(1) Note. This subclass does not include those systems wherein a filter or harmonic selecting network is provided for selecting a single frequency from the range of frequencies of the spectrum source, the selected frequency being fed to the comparator. Such systems are elsewhere in subclasses 1+, depending on the type of oscillator or type of A.F.S. control.

This subclass is indented under subclass 18. Subject matter wherein the oscillator system is of the type peculiarly adapted for use in television systems (e.g., vertical or horizontal sweep generators), the reference source comprising synchronizing pulses (usually of short duration) which pulses are compared with signals representative of the generated waves of the controlled oscillator in a phase comparison means, the resulting control or error signal from the comparison means being utilized to adjust the frequency of
the controlled oscillator to restore it to the desired relationship with reference frequency.

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subclasses 143+ for relaxation oscillators in general, especially indented subclass 145, for multivibrators with synchronizing, triggering or pulsing circuit, indented subclass 149, for blocking oscillators with synchronizing, triggering or pulsing circuit and indented subclass 153, for relaxation oscillators in general with synchronizing, triggering or pulsing circuit.

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315, Electric Lamp and Discharge Devices: Systems, subclasses 1+ for cathode-ray tube circuits, especially indented subclasses 378, 379+ and 391+ for cathode ray sweep circuits which may utilize sweep generators with A.F.S. control combined with significant cathode ray control means or cathode-ray tube structure, e.g., deflecting plates, deflecting coils, etc.
348, Television, subclasses 536+ for automatic frequency stabilizing systems as an element of a more comprehensive system, e.g., controlled oscillator combined with sync separator.
375, Pulse or Digital Communications, subclasses 354+ for synchronizers in general.

This subclass is indented under subclass 20. Subject matter wherein means are provided to stabilize or lock the controlled oscillator to the low frequency (e.g., 50, 60 C.P.S.) power current derived from a commercial alternating current supply line.

This subclass is indented under subclass 18. Subject matter wherein two or more frequency beating or heterodyning means, or stages, are effectively connected in the A.F.S. loop of the controlled oscillator.

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31 for oscillators with plural heterodyne stages in the A.F.S. loop, but wherein the discriminator is of the single input type, i.e., no comparison of the oscillator frequency with a reference frequency or source is made at the discriminator.
subclasses 38+ for beat frequency oscillator systems including plural beating or heterodyning means.

This subclass is indented under subclass 18. Subject matter wherein means are provided to frequency modulate the generated oscillations of the controlled oscillator by a low frequency reference source, signals representative of the modulated signal being compared with signals from the low frequency reference source in a signal comparator, the error signal from the output of the comparator being utilized to restore the generated frequency of the oscillator to the desired relationship with the reference frequency.

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4 for A.F.S. oscillators wherein the frequency of the oscillator is swept over a range of frequencies so as to bring the generated frequency within the "capture" range of the discriminator.

This subclass is indented under subclass 23. Subject matter wherein the signal comparator comprises a polyphase motor (usually of the two phase or split-phase type) having at least two phase windings, the signal representative of the low frequency modulated oscillations of the controlled oscillator being applied to one phase winding and the signal representative of the low frequency source being applied to another phase winding of the motor, the rotor of the motor is mechanically coupled to the frequency adjusting means of the oscillator.

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13 for a single oscillator with plural A.F.S. means wherein at least one of the A.F.S. means includes an electric motor for adjusting an oscillator frequency control means.
29 for A.F.S. oscillators with electromechanical signal comparator means.
35 for A.F.S. oscillators with electromechanical controlled oscillator frequency adjusting means.

This subclass is indented under subclass 18. Subject matter wherein a particular or significant signal or phase comparing network is utilized in the A.F.S. loop of the controlled oscillator.

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11 for single oscillator with plural A.F.S. means and including plural comparators.
32 for A.F.S. systems wherein the discriminator is of the single input type and wherein no signal comparison is made.

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324, Electricity: Measuring and Testing, subclass 76.52 for systems for measuring the frequency of a cyclic current or voltage by phase comparison with a standard cyclic current or voltage, and subclasses 76.77+ for systems for measuring electricity utilizing phase comparison means (e.g., phase comparison between cyclic pulse voltage and sinusoidal current).
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclasses 2+ for miscellaneous phase comparison circuits and subclasses 39+ for miscellaneous frequency comparing circuits.
329, Demodulators, subclasses 315+ for frequency demodulators and subclasses 345+ for phase demodulators.

This subclass is indented under subclass 25. Subject matter wherein the signal or phase comparator includes two or more unilaterally conducting devices (e.g., diodes) as elements thereof.

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33 for oscillator systems utilizing a single input, nonsignal comparing, discriminator of the plural diode type in the A.F.S. control loop thereof.

This subclass is indented under subclass 25. Subject matter wherein the signal of phase comparator includes two or more active elements (e.g., triodes) as elements thereof.

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324, Electricity: Measuring and Testing, subclass 89 for electric current or voltage measuring systems utilizing a phase comparator, a grid-controlled tube means constituting an element or elements thereof.

This subclass is indented under subclass 25. Subject matter wherein the signal or phase comparator includes a unilaterally conducting element (e.g., diode, triode) as an element thereof.

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324, Electricity: Measuring and Testing, subclasses 87+ for electric current or voltage measuring systems utilizing phase comparison means with nonlinear device (e.g., rectifier, grid controlled tube, etc.).

This subclass is indented under subclass 25. Subject matter wherein the signal or phase comparator is of the electromechanical type (e.g., two-phase motor, the reference source being applied to one phase winding and the controlled oscillator output being applied to the other phase winding) or a frequency comparing means of the synchroscope type.

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24 for A.F.S. controlled oscillators of the modulated oscillator type (e.g., frequency modulation of controlled oscillator) utilizing an electric motor comparator.

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324, Electricity: Measuring and Testing, subclass 90 for electric current and voltage measuring systems utilizing a phase comparator of the electrodynamometer type, and subclass 91 for phase comparators of the synchroscope type.

This subclass is indented under subclass 1. Subject matter wherein the A.F.S. loop of the controlled oscillator comprises (1) means for beating or heterodyning the generated oscillations of the controlled oscillator with the oscillations of the reference oscillator or source and (2) a single input discriminator means responsive to the resulting heterodyned oscillations, which discriminator produces an output error or control signal proportional to the frequency deviation of the controlled oscillator from that of the reference source, the error signal being utilized to restore the generated frequency of the controlled oscillator to the desired relationship with the reference frequency.

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subclasses 37+ for beat frequency oscillators, per se.

This subclass is indented under subclass 30. Subject matter wherein two or more beating or heterodyning means are utilized in the A.F.S. loop of the controlled oscillator.

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22 for oscillators having plural heterodyne stages in the A.F.S. loop, but wherein heterodyned oscillations of the controlled oscillator and the reference source signal are compared in a signal or phase comparator.
38 for beat frequency oscillator systems including plural beating or heterodyning means.

This subclass is indented under subclass 30. Subject matter wherein a significant or particular single-input frequency deviation detecting network or discriminator is utilized in the A.F.S. loop of the controlled oscillator.

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3 for A.F.S. systems utilizing a molecular resonance type discriminator.
9 for A.F.S. systems utilizing a distributed parameter type discriminator.
subclasses 25+ for A.F.S. systems wherein the discriminator is of the signal or phase comparing type, having at least two inputs for the signals (of the controlled oscillator and reference source) to be compared.

This subclass is indented under subclass 32. Subject matter wherein the frequency deviation detecting network or discriminator includes two or more unilaterally conducting devices (e.g., diodes) as elements thereof.

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26 for oscillator systems utilizing plural input signal or phase comparators of the plural diode type in the A.F.S. control loop thereof.

This subclass is indented under subclass 1. Subject matter wherein the controlled oscillator includes a significant or particular means for controlling, adjusting or varying its generated frequency as a function of the error signal from the discriminator in the A.F.S. loop of the controlled oscillator. The particular means may be (1) the adjustable tuning element of the controlled oscillator (e.g., a passive reactance or a reactance tube comprising an element of the oscillator tank circuit), or (2) the means for adjusting the tuning element of (1), (such as an electric motor drive therefor), or (3) the combination of (1) and (2).

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subclasses 177+ for oscillators in general with particular frequency adjustment means.

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333, Wave Transmission Lines and Networks, subclasses 219+ for resonators of the distributed parameter type which may be provided with frequency adjusting means.
334, Tuners, appropriate subclasses for tuners, per se. See the reference to Class 334 under subclass 1 above.

This subclass is indented under subclass 34. Subject matter wherein the frequency control means includes an electromechanical drive for the tuning or frequency adjusting element of the controlled oscillator.

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13 for a single oscillator with plural A.F.S. means and wherein electric motor means controls or adjusts the oscillator frequency determining means.
24 for A.F.S. controlled oscillators of the modulated oscillator type (e.g., frequency modulation of the controlled oscillator) utilizing an electric motor comparator.
29 for A.F.S. controlled oscillators having a signal or phase comparator of electromechanical type.

This subclass is indented under subclass 34. Subject matter wherein the particular frequency control means comprises an adjustable or variable reactance element or elements of the frequency determining network of the controlled oscillator. Examples of such elements are: reactance tubes, saturable core inductors, adjustable capacitors or inductors, etc.

This subclass is indented under the class definition. Subject matter comprising a signal producing system including a signal combining device (e.g., mixer, modulator) having signal input circuit means and a signal output circuit, at least two oscillators or a single oscillator simultaneously generating plural frequencies being connected to the input circuit means, the arrangement being such that the sum and/or difference frequencies (usually the difference frequency) of the oscillations generated by the respective oscillators or of the plural frequency oscillator appears in the output circuit of the signal combining means.
(1) Note. In addition to beat frequency oscillators the beat frequency principle is made use of in other systems. In general, beat frequency oscillators classified herein comprise means for beating two nonarbitrary sources of slightly different frequencies and of substantially equal amplitudes, the proximate purpose of the system being to produce a stable, high level, low frequency output wave (by selecting the lower side band). Modulators classified in Class 332 are directed to means for beating a source of carrier frequency of high amplitude with a signal wave of low amplitude, which signal wave varies arbitrarily in a continuous manner in accordance with some intelligence (e.g., sound). Radio receiver mixers or converters classified in Class 455, Telecommunications, are similar to the modulators of Class 332 except that the modulating signal wave contains, in addition to an arbitrary signal wave a large predictable component (the incoming carrier wave).

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19 for automatic frequency stabilized oscillators with a spectrum frequency reference source involving beat frequency generation in the stabilizing circuit.
22 for automatic frequency stabilized oscillators with signal comparator and having plural heterodyne stages in the stabilizing circuit.
subclasses 30+ for automatic frequency stabilized oscillators with a stable heterodyne oscillator or source.
51 for frequency divider systems comprising plural oscillators in cascade.
53 for frequency multiplier systems comprising plural oscillators in cascade.
76 for oscillators combined with an output coupling network, with space discharge device or unilaterally conductive device therein, for harmonic producing or selecting.

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307, Electrical Transmission or Interconnection Systems, subclass 424 for nonoptical parametric amplifier frequency converters, per se.
332, Modulators, see (1) Note above. Consult also the notes and search notes appended to the class and subclass definitions of Class 332 as to other fields of search for beat frequency systems.
359, Optics: Systems (Including Communication) and Elements, subclasses 326+ for optical frequency translators.
455, Telecommunications, subclasses 130+ for radio receivers using the beat frequency principle (in the form of autodyne, homodyne, superheterodyne and other types of beat reception), subclasses 313+ for radio receiver mixers or converters. See (1) Note above.

This subclass is indented under subclass 37. Subject matter wherein the system includes at least two signal combining means (i.e., mixers or modulators).

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22 for automatic frequency stabilized oscillators with reference oscillator or source and including plural heterodyne stages in the frequency control circuit.
31 for automatic frequency stabilized oscillators with plural heterodyne stages in the frequency control circuit.

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455, Telecommunications, subclasses 314+ for radio receivers that may have plural heterodyning stages.

This subclass is indented under subclass 38. Subject matter wherein the plural mixers or modulators are connected in concatenation or cascade in a single channel, that is, the output of one mixer is connected to the input of a succeeding mixer, etc.

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51 for frequency divider systems comprising plural oscillators connected in cascade.
53 for frequency multiplier systems comprising plural oscillators connected in cascade.

This subclass is indented under subclass 37. Subject matter wherein (1) means are provided for changing the generated frequency of at least one of the beating oscillators from one frequency to another, usually over a range of frequencies, the change may be by discrete steps or continuous over the range, or (2) means are provided for changing the amplitude of the generated oscillations of at least one of the beating oscillators or for effecting a change in amplitude at some other point in the system, e.g., in the mixer circuit.

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subclasses 1+ for oscillators which are automatically maintained on frequency by retuning means when the frequency drifts from the desired frequency, indented subclass 4 for search sweep of the oscillator, indented subclass 15 for amplitude compensated oscillator.
47 for plural oscillator systems wherein one oscillator varies the amplitude or frequency of another oscillator.
48 for plural oscillator systems wherein at least one oscillator has frequency adjusting means.
90 for magnetron type oscillators with frequency adjusting means.
109 for transistor oscillators with amplitude control.
subclasses 177+ for oscillators in general with frequency adjusting means.
subclasses 182+ for oscillators in general with amplitude adjusting means.

This subclass is indented under subclass 37. Subject matter wherein means are provided to prevent or compensate for an undesired drift in output frequency of the system. Such drift in frequency may be caused by (1) a change in a circuit parameter (due to ambient temperature variations or to the heating affects of currents in the circuit), (2) changes in active element characteristics, (3) changes in active element electrode potentials, (4) variations in load impedance, (5) undesired pull-in of one oscillator with respect to another oscillator of the system, etc.

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subclasses 1+ for oscillators of the automatic frequency stabilized type.
88 for magnetron type oscillators with means to stabilize the frequency.
subclasses 175+ for oscillators in general provided with frequency stabilizing means.

This subclass is indented under subclass 37. Subject matter wherein the signal combining means is of a particular type, such as the high frequency type (e.g., cavity mixer) or a tuned circuit between oscillator and mixer which circuit may include frequency dividers or multipliers.

This subclass is indented under subclass 42. Subject matter wherein a wave filter is included in the mixer output circuit.

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77 for oscillators with a wave filter connected in the output circuit.

This subclass is indented under the class definition. Subject matter (1) wherein means are provided to adjust the frequency setting means of the oscillator to make its frequency of oscillation correspond to the frequency (or fundamental, harmonic or sub-harmonic) of a source of standard frequencies or (2) means are provided wherein the frequency of the oscillations generated by the oscillator is compared with the frequency of the oscillations of a source of standard frequencies and the tuning position indicator or dial of the oscillator is graduated or marked in accordance with the results of the comparison with the known frequency setting or settings of the source of standard frequencies or (3) wherein means are provided to determine a performance characteristic, or characteristics, of the oscillator under prescribed conditions of operation (e.g., test under particular duty cycle, test under various load conditions, test purity of generated wave form, etc.).

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64 for oscillators with indicator, signal, or alarm in general and wherein frequency calibration of the oscillator with respect to a source of standard frequency or test of some other characteristic of the oscillator are not involved.

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250, Radiant Energy, subclass 250 for radio or microwave absorption wavemeters for determining the frequency or wavelength of a radio or microwave.
324, Electricity: Measuring and Testing, subclasses 20+ for systems for testing lamps and space discharge devices in general, particularly subclasses 24+ for testing the discharge characteristics of space discharge devices (e.g., such as triodes and pentodes), subclasses 57+ for measuring or testing electrical apparatus wherein no details of the apparatus are claimed, subclasses 76.12+ for systems to analyze complex electrical waves, and subclasses 76.39+ for systems for measuring the frequency of cyclic current or voltage.

This subclass is indented under the class definition. Subject matter wherein the oscillator system is provided with at least two output circuit, each output producing a separate
wave of the same frequency, the waves being displaced in phase by a fixed angle (other than phase coincidence or phase opposition) so as to produce a multiphase or polyphase set of currents or voltages.

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subclasses 50+ for plural oscillators connected in cascade wherein separate outputs may be taken from successive oscillators.
57 for ring oscillators comprising three or more switching tubes in closed ring connection.
60 for single oscillator systems provided with plural separate outputs.

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307, Electrical Transmission or Interconnection Systems, subclasses 13+ for polyphase systems in general.
363, Electric Power Conversion Systems, subclasses 1+ for cascaded or combined diverse conversion which may include conversion from one number of phases to another number of phases, and subclasses 148+ for phase conversion systems, per se.

This subclass is indented under the class definition. Subject matter comprising an electrical system including at least two significant oscillators.
(1) Note. If only one oscillator is significantly claimed and the other oscillator or oscillators are merely recited by name only without any oscillator circuit detail being claimed, classification is elsewhere in this class in accordance with the nature of system or of the significant oscillator claimed.

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subclasses 1+ for oscillator systems with automatic frequency stabilization which may involve plural oscillators. See especially subclasses: 2, wherein plural oscillators are stabilized, 18+, wherein a reference oscillator or source is utilized, 30+, for such systems combined with a stable heterodyne oscillator. 37+, for plural oscillators utilized
to produce a beat frequency. 45, for polyphase output systems that may utilize plural oscillators. 71, for oscillator systems wherein raw A.C. is utilized as a source of power or bias.
87 for magnetically controlled space discharge device oscillator (e.g., magnetron) with particular pulsing means.
106 for oscillators with periodic amplitude or frequency varying means (e.g., tremolo, vibrato).
145 for multivibrator oscillators with synchronizing, triggering or pulsing means.
149 for blocking oscillators with synchronizing, triggering or pulsing means.
153 for relaxation oscillators in general with synchronizing, triggering and pulsing means.
subclasses 172+ for oscillators in general with synchronizing, triggering or pulsing means.

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307, Electrical Transmission or Interconnection Systems, particularly subclasses 18+ for plural sources of electrical energy in general associated with plural output circuits and subclasses 43+ for plural sources of electrical energy associated with a common output or load.

This subclass is indented under subclass 46. Subject matter wherein means are provided to enable energy from one oscillator to modify or vary the amplitude or frequency of the oscillations generated by another oscillator.

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4 for automatic frequency stabilized oscillators wherein one oscillator sweeps the generated frequency of a frequency stabilized oscillator through a range of frequencies.
106 for oscillators with periodic or repetitious amplitude or amplitude and frequency varying means.
178 for oscillators with cyclic frequency sweeping means.

This subclass is indented under subclass 46. Subject matter wherein at least one of a plurality of oscillators is provided with means to change the generated frequency from one value to another.

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subclasses 1+ for plural oscillators with automatic frequency stabilization, and subclass 34+ for oscillators with automatic frequency stabilization having particular frequency control means.
40 for beat frequency oscillators with frequency adjusting means.
90 for magnetron type oscillators with frequency adjustment means.
106 for oscillators with periodic or repetitious frequency varying means.
subclasses 177+ for oscillators in general provided with frequency adjusting means.

This subclass is indented under subclass 46. Subject matter wherein means are provided for connecting one or more of two or more oscillators at will to a common output circuit or wherein means are provided for disconnecting one oscillator from a load circuit and connecting another oscillator to the load circuit, i.e., oscillator substitution.

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307, Electrical Transmission or Interconnection Systems, subclass 23 for systems for substituting a source in a plural source-plural load circuit system, subclass 29 for systems for selectively connecting plural sources to plural load circuits, subclasses 64+ for systems for substituting a source in a plural source-single load system, and subclass 80 for systems for selectively connecting a source or sources in a plural source-single load system.

This subclass is indented under subclass 46. Subject matter wherein two or more oscillators are effectively connected in concatenation, that is, the output circuit of one oscillator is connected to the input circuit of a second oscillator so that the first oscillator drives the second oscillator. The second oscillator may drive a third oscillator, the third oscillator a fourth oscillator, etc.

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subclasses 38+ for beat frequency oscillator systems wherein plural beating stages are cascaded.
subclasses 45+ for polyphase output oscillators which may utilize cascaded oscillators.
55 for plural oscillators wherein a periodic source, recited broadly, synchronizes, triggers or pulses at least one of the plural oscillators.

This subclass is indented under subclass 50. Cascaded oscillators wherein at least one succeeding oscillator generates oscillations of a frequency that is subharmonically related to the frequency of the oscillations generated by a preceding oscillator of the cascade.

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363, Electric Power Conversion Systems, subclasses 157+ for frequency conversion systems in general, wherein an input alternating current of one frequency is converted directly into an output alternating current of a different frequency. The output frequency may be either less or greater than this input frequency.

This subclass is indented under subclass 50. Subject matter
wherein the cascaded oscillators are of the semiconductor active element type (e.g., transistor).

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94.1 for molecular or particle resonant type oscillators which may utilize a semiconductor element.
subclasses 107+ for oscillators of the solid state active element type.

This subclass is indented under subclass 50. Cascaded oscillators wherein at least one succeeding oscillator generates oscillations of a frequency that is harmonically related to the frequency of the oscillations generated by a preceding oscillator of the cascade.

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76 for a single oscillator combined with an harmonic producing or selecting network, which network includes a space discharge or unilaterally conductive device.

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363, Electric Power Conversion Systems, subclasses 157+ for frequency conversion systems in general, wherein an input alternating current of one frequency is converted directly into an alternating current of another frequency. The output frequency may be either greater or less than the input frequency.

This subclass is indented under subclass 50. Subject matter wherein at least two of the cascaded oscillators are of different types, such as: Hartley and Colpitts oscillators, relaxation and sine wave oscillators, multivibrator and blocking oscillators, by way of examples.

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59 wherein a single oscillator system is provided with means to convert it from one type of oscillator to a diverse type.

This subclass is indented under subclass 46. Subject matter wherein at least one of a plurality of oscillators is provided with means for coupling the oscillator, or oscillators, to a periodic source of synchronizing or triggering potential to drive to lock the period of the oscillator, or oscillators, to the period of the source or to some multiple or submultiple thereof.

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subclasses 18+ for oscillators of the automatic frequency stabilized type synchronized with respect to a standard or reference frequency source.
41 for beat frequency oscillators that are locked to synchronize with a standard or reference frequency.
subclasses 50+ for cascade or tandem connected oscillators.
87 for magnetron type oscillators with means to pulse the oscillator.
145 for multivibrators with synchronizing, triggering or pulsing circuit.
149 for blocking oscillators with synchronizing, triggering or pulsing circuits.
153 for relaxation oscillators in general with synchronizing, triggering or pulsing means.
subclasses 172+ for oscillators in general with synchronizing, triggering or pulsing means.

This subclass is indented under subclass 46. Subject matter wherein the output circuits of at least two oscillators are effectively connected in parallel.

This subclass is indented under the class definition. Subject matter wherein the oscillator comprises three or more active elements connected or cascade, the output of one active element being connected to the input of another active element to form a closed chain or loop, the active elements being so connected and biased that they are caused to switch from a conducting to a nonconducting state in succession, cyclically, thereby generating self-sustained oscillations.

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45 for polyphase output oscillators which may be of the closed-ring type.
subclasses 50+ for plural oscillators connected in cascade.
113 for transistor oscillators of the multivibrator type wherein two transistors are alternately switched.
subclasses 135+ for phase shift oscillators which may comprise plural tubes in cascade in a closed loop, but wherein a switching action of the tubes does not take place.
subclasses 144+ for multivibrator oscillators in general wherein two tubes are alternately switched.

This subclass is indented under the class definition. Subject matter wherein the oscillator circuit is provided with means for performing at least one other function in addition to the generation of oscillations, which other function is independent of and is intended to be performed concurrently with the production of oscillations by the oscillator. An example of the type of plural function system falling within the foregoing definition is that of a vacuum tube circuit that simultaneously acts as an amplifier of extraneous waves of one frequency and as an oscillator with respect to waves of a different frequency, there being no mutual interaction between the two waves.

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subclasses 37+ for beat frequency oscillators wherein a single electron tube oscillator may act as a frequency converter, the oscillations generated by the oscillator being combined or mixed within the tube with externally supplied oscillations to produce in the output of the tube a beat frequency which is the algebraic sum or difference of the generated and supplied oscillations.
59 for oscillator systems that may be selectively converted from an oscillator to another type of electrical system, such as an amplifier, or detector, or to another oscillator of a different type.
subclasses 60+ for oscillators with plural output circuits, especially indented subclass 61 wherein the plural outputs are of diverse wave forms.

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330, Amplifiers, subclass 1, 82, 93, 101, 104, and 112 for subject matter including plural function amplifiers which also operate as oscillators simultaneously.
332, Modulators, appropriate subclasses, wherein a single electron tube circuit may perform the dual function of carrier frequency generation and modulation.
455, Telecommunications, subclasses 321+ for heterodyne receiving systems utilizing a frequency converter system wherein a single electron tube circuit may perform the dual function of local oscillation generation and signal frequency mixing.

This subclass is indented under the class definition. Subject matter wherein means are provided for effecting a change in oscillator circuit connections or for adding or substituting circuit element thereto so that the system resulting from such change or substitution is substantially different from the original oscillator circuit.
(1) Note. Typical systems classifiable herein are oscillators convertible to (1) amplifiers, (2) detectors, (3) wave meters, (4) triggered multivibrator, or oscillators convertible to another type of oscillator, for example, (5)
sine wave generator to square wave generator, (6) Colpitts oscillator to Hartley oscillator, (7) Colpitts oscillator to tuned feedback oscillator, and (8) fixed frequency crystal oscillator to tunable LC oscillator.

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58 for oscillator systems wherein the system simultaneously performs some function in addition to generating oscillations (e.g., amplifies an external signal or detects an external signal).
161 for crystal oscillators wherein means are provided for substituting one crystal for another in the oscillator circuit.
179 for oscillators in general wherein the frequency of oscillation is adjustable in discrete steps, e.g., by switching in or substituting inductors and/or capacitors having different fixed values of reactance.

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330, Amplifiers, subclass 1, 82, 93, 101, 104, and 112 for subject matter including amplifiers convertible to oscillators.

This subclass is indented under the class definition. Subject matter wherein the oscillator network includes at least two separate and distinct output circuits.
(1) Note. Push-pull output type oscillators for supplying a balance push-pull load are classified with the particular oscillator.

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45 for oscillators of the polyphase output type wherein the separate output voltages or currents are of the polyphase type, i.e., the separate output voltages or currents are of the same period and differ by a constant phase angle (other than phase coincidence or phase opposition).
subclasses 46+ for plural oscillator systems which may have plural separate outputs.
subclasses 74+ for oscillators combined with a particular
output coupling network which network may include plural separate output circuits.

This subclass is indented under subclass 60. Subject matter wherein the electric waves derivable from at least two separate output circuits are of different wave shapes. Examples are: sine wave and triangular wave, saw-tooth and square wave, sine wave and square wave, etc.

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75 for oscillators with space discharge device or unilaterally conductive device in the output circuit (e.g., for producing distorted waves).
subclasses 111+ for transistor-type relaxation oscillators.
subclasses 129+ for gas-tube type relaxation oscillators.
subclasses 143+ for relaxation oscillators in general.

This subclass is indented under the class definition. Subject matter wherein the oscillator is provided with means to protect the oscillator circuit or elements thereof from damage due to some condition or malfunction of the oscillator circuit or power supply therefor.

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63 for oscillators provided with means to protect operating personnel or others who may come into contact with exposed portions of the oscillator from electrical shock.
67 for oscillators provided with electromagnetic or electrostatic shield means to prevent undesirable couplings between elements of the oscillator caused by fields generated within the oscillator circuit or to prevent external fields from influencing the oscillator.
subclasses 68+ for oscillators having outer casings or housings to protect the oscillator from damage due to external mechanical forces.
70 for oscillators provided with means to modify the temperature of the oscillator or elements thereof, wherein the means may be for the purpose of cooling the oscillator or elements thereof to prevent damage thereto that would result if the oscillator or elements thereof were permitted to overheat.
subclasses 182+ for oscillators having means for controlling or maintaining the amplitude level of the generated oscillations and wherein the invention is not primarily for protecting the oscillator from overload.
186 for oscillators having a regulated source of power or bias and wherein the invention is not primarily for protecting the oscillator from damage due to excessive bias potential.

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307, Electrical Transmission or Interconnection Systems, subclasses 326+ for electrical systems in general having self-protective, safety or limit control features.
361, Electricity: Electrical Systems and Devices, subclasses 1+ for safety and protection systems for electrical devices and equipment in general. See the search notes, and under "SEARCH CLASS" of subclasses 92+ of Class 307 and subclasses 1+ of Class 361 as to further fields of search for protective systems for specific electrical devices and systems.

This subclass is indented under the class definition. Subject matter wherein the oscillator is provided with means for protecting persons contacting the oscillator or an exposed portion thereof or persons controlling the oscillator from the danger of bodily injury or electrical shock because of the high potentials associated with the oscillator (e.g., the potential of the power source or the generated oscillations).

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62 for oscillators having means to prevent damage to the
oscillator circuit or elements thereof due to some condition or malfunction of the oscillator circuit or the power supply therefor.
subclasses 68+ for oscillators with protective casings or housings.

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174, Electricity: Conductors and Insulators, subclass 5 for electric shock hazard protective devices in general. See also the search notes to this subclass as to other fields of search for devices to protect personnel against electrical shock.

This subclass is indented under the class definition. Subject matter wherein the oscillator is provided with an indicator, signal or alarm means to indicate or signal some state or condition of the oscillator.
(1) Note. Examples of indicating, signaling or alarm means included herein are (1) calibrated scales and cooperating indicators or pointers to indicate the frequency setting of a tunable tank circuit of the oscillator or to indicate the amplitude setting of an output attenuator of the oscillator, (2) electric meters, signals or alarms to indicate or respond to any current or potential of the oscillator, such as output load current or power, overload current, bias potential level, frequency of the generated oscillations, standing wave ratio of oscillator resonator, etc., (3) indicating or signaling means responsive to any other condition of the oscillator such as temperature or humidity, by way of example.
(2) Note. Systems wherein the oscillator is an element of a more comprehensive indicating or signaling system, for example, a system for performing an external (to the oscillator) chemical, physical or electrical measurement or test are not classified herein but in the class providing for such systems.

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44 for methods of or systems for calibrating the oscillation frequency setting means or tuning scale of an oscillator or for testing the oscillation frequency characteristics of the oscillator.

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73, Measuring and Testing, appropriate subclasses for physical measuring and testing systems or devices in general not elsewhere provided for.
116, Signals and Indicators, appropriate subclasses for indicators, signals and alarms of the mechanical type and not elsewhere classifiable.
250, Radiant Energy, subclass 250 for radio and microwave absorption meters for determining the wavelength or frequency of a radio or microwave.
324, Electricity: Measuring and Testing, appropriate subclasses for electrical measuring and testing systems in general, particularly subclass 76.39 for cyclic current or voltage frequency measuring or testing devices.
332, Modulators, subclass 118 for frequency modulators and subclass 150 for amplitude modulators with indicating means, observing means and/or signal, respectively.
340, Communications: Electrical, appropriate subclasses for electrical signals and alarms, especially subclass 870.01 for continuous variable indication devices and systems (e.g., telemetry) and subclass 653 for oscillator condition responsive signals and alarms.

This subclass is indented under the class definition. Subject matter wherein the oscillator is combined with means distinct from the oscillator system or wherein the means is a modified element of the oscillator, which means is responsive to a nonelectrical condition external to the oscillator, a current characteristic of the oscillator, (e.g., amplitude or frequency) being varied in accordance with changes in the sensed condition.
(1) Note. The condition sensing means may, for example, comprise means responsive to (1) presence or absence of a material body, (2) moisture or humidity, (3) temperature, (4) light, (5) pressure, (6) liquid level, and so forth.

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subclasses 1+ for oscillators with automatic frequency stabilization wherein means are employed to sense a drift in oscillator frequency and to effect a tuning of the oscillator in the proper direction to maintain the oscillator frequency constant.
62 for oscillators having means to sense an undesirable condition in the oscillator and responsive thereto to correct the condition or so control the oscillator to prevent damage to the oscillator.
69 and 70, for oscillators having means to modify the temperature of the oscillator or a part thereof in response to temperature changes in the oscillator or the relative temperature change of the oscillator and its ambient medium.
176 for oscillators whose frequency is stabilized by a temperature or current responsive means in the oscillator circuit.

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73, Measuring and Testing, appropriate subclasses, for measuring and testing apparatus involving sensing means for making physical measurements or tests not provided for in other classes. See also, the Notes to the class definitions and under "SEARCH CLASS" as to condition sensing means classified in other classes. See particularly under (3) Note, section C, of the class definition of Class 73 as to various electrical devices and electrical systems classes which utilize condition responsive controls.
332, Modulators, appropriate subclasses for modulated oscillators combined with specific intelligence source (e.g., electro-acoustic transducer).
369, Dynamic Information Storage or Retrieval, subclass 129 for a phonograph circuit with an information modulated oscillator.

This subclass is indented under subclass 65. Subject matter wherein the condition responsive means is responsive to temperature or radiant energy in the form of light.

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176 for frequency stabilized oscillators with temperature or current responsive stabilizing means in circuit.

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250, Radiant Energy, subclasses 200+ for visible light responsive photocell electric circuits or photocell apparatus in general.
332, Modulators, appropriate subclasses for modulated
oscillators combined with a specific intelligence source of the photoelectric transducer type.
340, Communications: Electrical, subclasses 584+ and 600 for electrical signal systems or alarms responsive to temperature, radiant and energy respectively.
356, Optics: Measuring and Testing, subclasses 43+ for optical pyrometers, subclasses 402+ for shade or color testing, and subclasses 213+ for photometers.
374, Thermal Measuring and Testing, subclasses 121+ for a thermal radiation responsive thermometer, and subclasses 170+ for an electrical thermometer with a digital signal controlling an indicator.

This subclass is indented under the class definition. Subject matter wherein the oscillator system is provided (1) with means for shielding at least part of the oscillator system from external electric or magnetic fields, (2) with means to shield one or more parts of the oscillator system from electric or magnetic fields generated in one or more other parts of the oscillator system, (3) with shielding or screening means to prevent radiation of undesired electric or magnetic fields generated within the oscillator system.
(1) Note. The electric or magnetic shield or screen to be classified herein must be in addition to and separate from oscillator circuit element structure. For example, if the electron tube of the oscillator contains a screen grid orshielding electrode as a perfecting feature of the tube this is considered tube structure and not shielding or screening for this subclass. Subclasses 72+ for instance, is directed to electron coupled oscillators utilizing tetrode or pentode tubes wherein the screen electrode shields or screens the oscillator circuit section of the tube from the output or anode circuit thereof. Another example of excluded subject matter is that of an oscillator wherein the resonator of the oscillator encloses and forms a screen for the active element of the oscillator (see subclasses 97+, for example, for a tube enclosed by a distributed parameter type resonator).
(2) Note. The shield or screen must be claimed as a magnetic, electric or electromagnetic shield or screen, or such limitations must be recited to clearly restrict the shield or screen to that use, to cause classification in this subclass. Merely reciting the combination of an oscillator with an outer casing or housing, or as a metallic outer casing or housing, for example, would not be sufficient for classification herein, such combination being classified in subclasses 68+ below.

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subclasses 68+ for oscillators combined with outer casing or housing. See (2) Note above.
subclasses 72+ for electron coupled oscillators utilizing screen grid tubes. See (1) Note above.
subclasses 79+ for beam tube oscillators wherein part of the tube structure may include electric or magnetic shielding means.
subclasses 86+ for magnetically controlled space discharge device oscillators wherein part of the discharge device may include electric or magnetic shielding means.
subclasses 97+ for oscillators wherein the oscillator tube is enclosed by a distributed parameter resonator of the oscillator. (See (1) Note above).

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174, Electricity: Conductors and Insulators, subclasses 32+ for miscellaneous anti-inductive structures, see particularly indented subclasses 35+, for miscellaneous electrical shields and screen structures not elsewhere classifiable. The search notes to subclasses 32+, indicate further fields of search for anti-inductive and shielding structure.

This subclass is indented under the class definition. Oscillators provided with a casing or housing to enclose the oscillator.
(1) Note. The function of the casing or housing surrounding the oscillator in the patents in this subclass is to provide primarily for the mechanical protection or for the control of the physical environment of the enclosed oscillator.
(2) Note. The casing or housing includes at least the
oscillator system and may or may not include the power supply or biasing sources for the oscillator.
(3) Note. If the casing or housing is claimed as an electric, magnetic, or electro-magnetic shield or screen the patent is excluded.
(4) Note. The casing or housing in this subclass must be independent of the oscillator. For example, if the oscillator is enclosed by one of its own components (such as its resonator) classification is with the particular oscillator.

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67 for oscillators with electromagnetic or electrostatic shield. See (3) Note above.
subclasses 79+ for beam tube oscillators wherein the frequency determining structure (i.e., resonator or slow wave structure) is enclosed by the tube envelop.
subclasses 86+ for magnetically controlled space discharge device oscillators (e.g., magnetron) wherein the frequency determining network of the oscillator is enclosed by the tube envelope.
subclasses 97+ for oscillators wherein the active element is enclosed by a distributed parameter resonator. See (4) Note above.

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174, Electricity: Conductors and Insulators, for miscellaneous casings and housings for electrical devices and including the combination of the casing or housing with the electrical device recited by name only, particularly subclasses 8+ for such devices intended to be used with a fluid or vacuum and subclasses 50+ for such devices of general utility. See the search notes to the class definition of Class 174 and to subclasses 8 and 50 and under "SEARCH CLASS" thereunder as to other fields of search for particular electrical devices with housings.

This subclass is indented under subclass 68. Subject matter
wherein means are associated with the housed oscillator for controlling or modifying the temperature of the oscillator or elements thereof.

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66 for oscillators combined with temperature sensing means external to the oscillator for controlling a characteristic of the oscillator (e.g., frequency or amplitude) as a function of an externally sensed temperature.
70 for oscillators having means for controlling or modifying the temperature of the oscillator or elements thereof and wherein the oscillator is not combined with an enclosing housing or casing.

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174, Electricity: Conductors and Insulators, subclass 15.1 for combined electrical device (recited by name only) casing or housing therefor and means for feeding, circulating or distributing a fluid or with means to cool either the electrical device or the fluid.

This subclass is indented under the class definition. Subject matter wherein means are provided for modifying or controlling the temperature of the oscillator or elements thereof.
(1) Note. For example, included in this subclass are oscillators provided with (1) crystal ovens for controlling or maintaining the oscillator crystal temperature constant, (2) means for forcing a cooling fluid through a cavity resonator of the oscillator, (3) means for circulating a fluid through a hollow conductor comprising the inductor of the LC frequency determining element of the oscillator, (4) an oscillator tube wherein the anode or cathode structure of the tube is provided with passages through which a cooling fluid is passed or wherein the external terminal of the anode electrode may include cooling fins.

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66 for oscillators combined with an external temperature responsive means for controlling a characteristic (e.g., frequency or amplitude) of the oscillator.
69 for oscillators including temperature modifying means, combined with an outer casing or housing.
176 for oscillators in general including temperature or
current responsive means in the oscillator circuit for stabilizing the oscillator frequency.

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174, Electricity: Conductors and Insulators, subclass 15.1 for means for cooling electrical apparatus wherein no details of the apparatus are claimed. See the search notes to subclass 15.1 and the class definition search notes of Class 174 for other fields of search with respect to modifying the temperature of particular electrical apparatus.

This subclass is indented under the class definition. Subject matter wherein the source of power or bias for the output and control electrodes or the output electrode of the active element of the oscillator comprises raw alternating current, which current is applied directly to the electrodes.
(1) Note. Where the raw alternating current is merely applied to the control electrode of the active element of the oscillator classification is not in this subclass, but elsewhere in this class in accordance with the particular type of oscillator systems or the nature of the control. See the search notes below for oscillator systems which may have alternating current applied to the control grid of the active element thereof may be found, wherein one oscillator is used to vary the amplitude of the oscillation generated by another oscillator; for cascaded or series connected oscillators; for a subclass wherein plural oscillators may be synchronized from an external source or where one oscillator synchronizes another; for oscillators with periodic or repetitious amplitude and/or frequency varying means (e.g., tremolo, vibrato); for and oscillators with synchronizing triggering or pulsing means involving grid bias control ; for blocking oscillators, for relaxation oscillators in general and for oscillators in general.

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47 for oscillator systems which may have alternating current applied to the control grid of the active element thereof, wherein one oscillator is used to vary the amplitude of the oscillation generated by another oscillator.
subclasses 50+ for cascaded or series connected oscillators.
55 wherein plural oscillators may be synchronized from an external source or where one oscillator synchronizes another
106 for oscillators with periodic or repetitious amplitude and/or frequency varying means (e.g., tremolo, vibrato).
145 oscillators with synchronizing triggering or pulsing means involving grid bias control may be found in this subclass (145) for multivibrators
149 for blocking oscillators.
153 for relaxation oscillators in general
subclasses 172+ for oscillators in general..
subclasses 185+ for oscillators with particular source of power or bias voltage.

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315, Electric Lamp and Discharge Devices: Systems, subclasses 137+ for gaseous space discharge device or vacuum diode systems supplied with a polyphase alternating current, and subclasses 246+ for similar systems supplied with pulsating or alternating current supply (see the search notes appended to subclasses 246+ for further fields of search for similar subject matter).
330, Amplifiers, subclasses 114+ for linear amplifiers wherein an unrectified alternating current is applied to an electrode of an active element or elements, thereof.

This subclass is indented under the class definition. Subject matter wherein the active element of the oscillator includes a cathode, two or more grids and an output electrode (e.g., conventional tetrode or pentode) and wherein the cathode and at least two grids are connected in circuit to form a triode oscillator, one of the grids acting as an anode electrode, and wherein the output electrode is coupled to the oscillator solely through the electron stream, so that the output circuit is substantially isolated from the oscillator circuit. In effect, the resulting circuit comprises an oscillator and power amplifier combined in one tube.

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subclasses 75+ for the combination of oscillator and output amplifier, wherein the oscillator and amplifier each comprise separate and distinct active elements.
subclasses 79+ for beam tube type oscillators wherein the output circuit may be electron coupled to a directed electron beam.
134 for negative resistance oscillators of the transition type wherein a plural grid active element is utilized.
147 for blocking oscillators utilizing a plural grid tube.
152 for relaxation oscillators having a multi-grid discharge device in the charged capacitor circuit.

This subclass is indented under subclass 72. Subject matter, wherein a piezoelectric crystal comprises a frequency determining element of the oscillator.

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116 for transistor oscillators using a piezoelectric crystal.
139 for bridge oscillator with piezoelectric crystal in the bridge network.
155 for oscillator with a crystal driven e