(A) This is the generic class for amplifiers as limited by the definition of amplifiers as it appears in the Glossary below.
(B) Included are amplifiers having all types of active elements (or amplifying devices, the term used in this class) as for example vacuum tubes, gas tubes, semiconductors, magnetic type saturable reactors, masers, etc.., as set forth in the specific subclasses in the schedule for the class. Specific types of vacuum tube amplifier devices included are, traveling wave type tubes, secondary emission type tubes, electron beam tubes, magnetrons, etc..
(C) Included are amplifier systems having plural amplifier channels, cascade amplifiers, push-pull amplifiers and other amplifiers having plural amplifier devices. Also included are amplifiers with plural signal sources or plural loads, as for example sum or difference amplifiers which have plural sources.
(D) Amplifiers including the means coupling the signal source to the amplifier or coupling the amplifier to the load or between cascaded stages are also included herein. Such coupling means include those of the distributed parameter type, resonant tuned circuits, filters, coupling designed to pass a broad band, D.C.. coupled circuits, potentiometer means for volume control, equalizers, circuits for volume control, etc..
(E) Amplifiers combined with tone control means are also included herein as indicated in D above for the type included in the amplifier coupling means, also included herein are those tone control amplifiers relying on signal feedback means to effect the tone control.
(F) Amplifiers combined with amplitude (volume) control means whether by manual control, by control of an electrode D.C.. bias, as in gain control, or by controlling a variable impedance means for the signal transmission path of the amplifier are also included herein.
(G) Amplifiers combined with power supply means for such amplifier are also included herein, as well as means to control the voltage or current of such means.
(H) Amplifiers combined with structural features of the amplifier or the amplifier circuit elements including structure of the amplifier device, capacitors, transformers, etc..
(I) Amplifiers having signal feedback means.

LINES WITH OTHER CLASSES AND WITHIN THIS CLASS
A. TWO-TERMINAL NEGATIVE RESISTANCE NETWORKS
Such networks containing an active element (amplifying device) are not classified in this class, but classified elsewhere. (See References to Other Classes, below.)
B. LIMITERS
Passive networks which limit the signal amplitude voltage or current are classified elsewhere. Miscellaneous limiting circuits with active device elements are classified elsewhere. (See References to Other Classes, below.)
C. MISCELLANEOUS ELECTRONIC TUBE CIRCUITS
Circuits including electron tubes (other than the limiters discussed above) in which the signal output is not a substantial replica of the input signal, are classified residually elsewhere. Examples of such tube circuits are wave conversion circuits, miscellaneous pulse generating systems, and electronic tube gating circuits. (See References to Other Classes, below.)
D. SATURABLE REACTOR CIRCUITS (MAGNETIC AMPLIFIERS)
Such circuits which control voltage or current and are not classifiable herein (as for example, where the A.C. power supply current is not removed from the signal output by filtering or other means) are classified elsewhere. Saturable reactor circuits for wave shaping, switching, pulse production, etc.., analogous to similar electronic tube circuits are classified elsewhere with nonlinear reactor systems, and computers using magnetic amplifiers are also classified elsewhere. (See References to Other Classes, below.)
E. NONLINEAR REACTOR CIRCUITS:
Where a nonlinear capacitor serves as the active element or amplifying device in a circuit which switches, shapes a wave, or produces pulses and is not provided for elsewhere classification is in Class 307. So called amplifier circuits including a nonlinear capacitor as the amplifying device, which have an A.C. source where the claims do not provide a filter to remove the A.C. source from the output or where a demodulator is claimed and no filter or other means to remove the A.C. power supply from the signal output circuit is disclosed, are excluded from this class. (See References to Other Classes, below.)
F. MISCELLANEOUS TRANSISTOR CIRCUITS:
Transistor circuits which are not amplifiers or not combined with an art device or in a system specifically provided for in some class, are classified elsewhere. Such art as miscellaneous transistor wave shapers, gating circuits, limiters, and pulse producers are classified therein. (See References to Other Classes, below.)
G. AMPLIFIER COMBINED WITH SPECIFIC SOURCE OF SIGNAL ENERGY:
This class does not provide for combinations of amplifiers with a specific source of electric signal, such as a microphone which limits the system to use with a particular art even though the source is claimed by name only. Similarly, where the source is claimed by characteristics specific to the art device as for example, "a source of speech signals" classification is not in this class. However, classification is in this class where the source is claimed by its electrical characteristics not specific to the source device, as for example, "a high impedance source of electrical signal". Where the specific source, or details thereof are claimed, classification is with the art device so identified. (See References to Other Classes, below.)
Generator Or Oscillator Claimed By Name Only
The terms generator or oscillator in claims, where they appear as sources of signal energy without further qualification except by their electrical characteristics such as impedance, reactance, etc.., are treated as generalized sources of signal energy, and classification is with amplifiers except where specific details of the generator or oscillator are claimed; in such cases classification is with the type of generator claimed or with oscillators. (See References to Other Classes, below.)
H. AMPLIFIERS COMBINED WITH SPECIFIC LOAD:
Where the load is claimed, broadly, or by name only as a specific electrical art device, as for example, as a loudspeaker, classification is not in this class but with the load art device claimed. Where characteristics of the load device are claimed, which are peculiar to the disclosed electrical art device or to a specific type of electrical art device, classification is with the load art device established in the claim. Subject matter wherein general electrical characteristics of the load are claimed, as for example, "a load having a variable impedance," is classified in this or indented subclasses. (See References to Other Classes, below)
I. OSCILLATOR AS A LOAD FOR AN AMPLIFIER
Subject matter wherein an amplifier is combined with an oscillator as load for the amplifier is classified with amplifiers when the oscillator is claimed by name only; where specific details of the oscillator are claimed, classification is elsewhere. (See References to Other Classes, below.)
J. REPEATERS:
Devices known in the art as repeaters which are in effect two-way amplifiers are not classified in this class but are classified elsewhere. (See References to Other Classes,
below.)
K. AMPLIFIERS COMBINED WITH LONG LINE TRANSMISSION MEANS OR DISTRIBUTED PARAMETER ELEMENTS, AND AMPLIFIERS COMBINED WITH WAVE FILTERS, EQUALIZERS OR ATTENUATORS:
Such subject matter is classified herein even though the amplifier is claimed by name only, if some detail of the co-operation of the amplifier with the passive network (coupling) is claimed. (See References to Other Classes, below.)
L. COMPANDERS INCLUDING AMPLIFIERS:
Systems including means to compress a signal wave, an electrically long transmission line and means to expand the signal wave are not classified herein even when they include details of an amplifier. Companders are classified elsewhere. Amplifiers with compressor or expander means alone not involving a complete compander system are classified herein. Such subcombinations involving connection or maintenance of a predetermined condition of the transmission line are classified elsewhere. Where such connection is of an amplifier condition classification is herein. (See References to Other Classes, below.)
M. SYSTEMS INCLUDING PILOT CONTROL MEANS:
Amplifiers including a pilot control frequency component in the signal source which is used to control the amplifier are classified herein.
Transmission Lines Combined With Pilot Control - Such subject matter is classified elsewhere when provided with an auxiliary line for the pilot control signal; for those systems in which the pilot control signal is combined with the signal to be transmitted; with an amplifier which is controlled must correct or maintain a predetermined condition of the transmission line for classification elsewhere. Otherwise classification is herein.
Pilot Frequency Controlled Repeaters - Such subject matter is classified elsewhere.
N. GAS OR VAPOR TUBE CIRCUITS IN OTHER CLASSES:
Gas or vapor tube circuits are classified elsewhere. (See References to Other Classes and Within This Class.)
O. TRAVELING WAVE TUBES AND CIRCUITS:
Classification of traveling wave tube amplifiers is in this class when it includes the output or load circuit. Classification is otherwise where no load or output circuit is claimed and the circuit means which may be involved are an integral part of the tube. Oscillators including a traveling wave tube are classified elsewhere. (See References to Other
Classes, below.)
P. AMPLIFIER AND A DETECTOR OR SUPERHETERODYNE CONVERTER AND AN AMPLIFIER:
Such subject matter involves a subcombination peculiar to radio receivers and is classified elsewhere with radio receivers or in appropriate subclasses for a demodulator with amplifier. When an amplifier and a detector are claimed and the detector is claimed merely as a means to develop a control signal and not for the purpose of detecting the intelligence signal as a function of a receiver, classification is herein and not in receivers. Where the same tube serves both as a detector and an amplifier classification is not in this class but elsewhere. Demodulators, depending again upon the type of demodulator involved, are classified elsewhere. Combinations which comprise a reflex amplifier or a superregenerative detector are classified elsewhere. (See References to Other Classes, below.)
Q. VOLTAGE MAGNITUDE CONTROL SYSTEMS:
Voltage magnitude control (for single source energy systems) such as line voltage control, etc.., in general, is classified elsewhere and includes current or load regulation, current and voltage limiting systems, transformer and impedance systems for the purpose. See LIMITERS, above. (See References to Other Classes, below.)
R. SYSTEM OR DEVICES CLOSELY RELATED TO OR ANALOGOUS TO AMPLIFIERS:
See References to Other Classes, below.
S. SYSTEMS UTILIZING AMPLIFIERS:
The great majority of electrical control or signaling systems utilize amplifiers such as are classified herein or closely related devices (as where the waveform of the input is not retained in the output). Such systems include, also, mechanical systems with electrical control means. In view of such widespread use no attempt is made to list the classes of all or a large number of systems utilizing amplifiers. Systems involving amplifiers in combinations where the amplifier is invariably present, involve few additional elements, or wherein the amplifier is usually an important component of the combination are classified elsewhere.
Also see References to Other Classes, below.
T. ELEMENTS OR CIRCUIT NETWORKS COMMONLY USED IN AMPLIFIERS OR AMPLIFIER SYSTEMS:
See References to Other Classes, below.

REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, 32 for shielding means. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers," above.)
250, Radiant Energy, appropriate subclasses, for the detection of invisible radiant energy or the testing of materials by invisible radiant energy, 200 for photocell circuits and apparatus, particularly subclass 214 for photocell controlled circuits including electron tube circuits. (See Lines With Other Classes, S, "Systems Utilizing Amplifiers," above.)
257, Active Solid-State Devices (e.g., Transistors, Solid-State Diodes), for active solid state devices, per se. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers or Amplifier Systems, " above.)
307, Electrical Transmission or Interconnection Systems, for saturable reactor circuits for wave shaping, switching, pulse production, etc.., analogous to similar electronic tube circuits; 401 for nonlinear reactor systems. So called amplifier circuits including a nonlinear capacitor as the amplifying device, which have an A.C. source where the claims do not provide a filter to remove the A.C. source from the output or where a demodulator is claimed and no filter or other means to remove the A.C. power supply from the signal output circuit is disclosed is classified in subclasses 401+. (See Lines With Other Classes, D, "Saturable Reactor Circuits (Magnetic Amplifiers)." E, "Nonlinear Reactor Circuits." and R, "System or Devices Closely Related to or Analogous to Amplifiers," above.)
313, Electric Lamp and Discharge Devices, appropriate subclasses for the structure of vacuum tubes and gas and vapor tubes. See the class definition of Class 313. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers", above.)
315, Electric Lamp and Discharge Devices: Systems, for gas or vapor tube circuits in other classes; see the classes specified in the Notes thereto for gas or vapor tube circuits. (See Lines With Other Classes, N, "Gas or Vapor Tube Circuits in Other Classes.")
315, Electric Lamp and Discharge Devices: Systems, subclass 3.5, 3.6 or 39.3 for classification otherwise where no load or output circuit is claimed and the circuit means which may be involved are an integral part of the tube. (Lines With Other Classes, O, "Traveling Wave Tubes and Circuits")
323, Electricity: Power Supply or Regulation Systems for passive networks which limit the signal amplitude voltage or current. (Lines With Other Classes, B, "Limiters.")
323, Electricity: Power Supply or Regulation Systems, for circuits which control voltage or current. (See Lines With Other Classes, D, "Saturable Reactor Circuits (Magnetic Amplifiers.")
323, Electricity: Power Supply or Regulation Systems, for voltage magnitude control (for single source energy systems) such as line voltage control, etc.., in general (see the class definition). (Lines With Other Classes, "Voltage Magnitude Control Systems")
324, Electricity: Measuring and Testing, 123 for amplifiers with meters.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 309 for miscellaneous limiting circuits with active device elements.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 100 for wave conversion circuits, subclasses 291+ for miscellaneous pulse generating systems, and subclasses 365+ for electronic tube gating circuits. (Lines With Other Classes, C, "Miscellaneous Electronic Tube Circuits.")
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for transistor circuits which are not amplifiers or not combined with an art device or in a system specifically provided for in some class. (See Lines With Other Classes, F, "Miscellaneous Transistor Circuits.")
329, Demodulators, appropriate subclasses for a demodulator with amplifier. (See Lines With Other Classes, P, "Amplifier and a Detector or Superheterodyne Converter and an Amplifier" and S,"Systems Utilizing Amplifiers", above.)
329, Demodulators, where the same tube serves both as a detector and an amplifier, depending upon the type of demodulator involved. (Lines With Other Classes, P, "Amplifier and a Detector or Superheterodyne Converter and an Amplifier")
331, Oscillators, are in the most common types, in a sense, merely positive feedback amplifiers without an input, and therefore the circuits, structures, and problems are often closely related to those of amplifiers. (See Lines With Other Classes, R, "System or Devices Closely Related to or Analogous to Amplifiers, " above.)
331, Oscillators, where specific details of the generator or oscillator are claimed; in such cases classification is with the type of generator claimed or with oscillators. (See Lines With Other Classes, G, under "Generator or Oscillator Claimed by Name Only," and I, "Oscillator as a Load for an Amplifier, " above.)
331, Oscillators, for oscillators including a traveling wave tube; subclass 82 for traveling wave type. (Lines With Other Classes, O, "Traveling Wave Tubes and Circuits")
332, Modulators, appear, usually as no more than amplifiers which have an input source in addition to the signal (i.e., the carrier). (See Lines With Other Classes, R, "System or Devices Closely Related to or Analogous to Amplifiers", above.)
333, Wave Transmission Lines and Networks, appropriate subclasses, particularly 24, for passive wave filters and coupling networks. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers or Amplifier Systems," above.)
333, Wave Transmission Lines and Networks, 213 for networks containing an active element (amplifying device). (See Lines With Other Classes, A, "Two-Terminal Negative Resistance Networks," above.)
333, Wave Transmission Lines and Networks, subclass 14 for companders. Subcombinations involving connection or maintenance of a predetermined condition of the transmission line are classified in Class 333. (See Lines With Other Classes, L, "Companders Including Amplifiers.")
333, Wave Transmission Lines and Networks, subclass 15, when provided with an auxiliary line for the pilot control signal, subclass 16 for those systems in which the pilot control signal is combined with the signal to be transmitted and also subclass 16 with an amplifier which is controlled must correct or maintain a predetermined condition of the transmission line. (Lines With Other Classes, M, under "Transmission Lines Combined With Pilot Control," above.)
333, Wave Transmission Lines and Networks, for electric wave transmission systems, passive wave transmission networks, passive coupling networks and terminating networks, smoothing type wave filters, networks including a wave transmission device, passive networks for producing an output wave, systems including active elements, and wave traps using long line elements. (Lines With Other Classes, K, "Amplifiers Combined With Long Line Transmission Means or Distributed Parameter Elements, and Amplifiers Combined With Wave Filters, Equalizers or Attenuators")
334, Tuners, appropriate subclasses for tuners, per se. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers, " above.)
336, Inductor Devices, appropriate subclasses for the structure of transformers and inductor devices, generally. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers or Amplifier Systems, " above.)
359, Optics: Systems (Including Communication) and Elements, 109 for light wave communications. (See Lines With Other Classes, S, "Systems Utilizing Amplifiers," above.)
361, Electricity: Electrical Systems and Devices, 196 for electric circuits including transistors, subclasses 199+ and 205 for electric circuits including space discharge devices combined with relays as the load therefor, and subclass 204 for electric circuits including saturable reactors, wherein the transistor, space discharge, or saturable reactor circuit may be an amplifier. (See Lines With Other Classes, S, "Systems Utilizing Amplifiers", above.)
361, Electricity: Electrical Systems and Devices, 271 and 500+ for capacitor structure, per se. (See Lines With Other Classes, T, "Elements or Circuit Networks Commonly Used in Amplifiers or Amplifier Systems," above.)
379, Telephonic Communications, 338 for devices known in the art as repeaters which are in effect two-way amplifiers. (See Lines With Other Classes, J, "Repeaters," above.)
381, Electrical Audio Signal Processing Systems and Devices, 111 for miscellaneous systems which include combinations of amplifier and loud speaker or microphone and amplifier which limits the system to use with a particular art even though the source is claimed by name only; for distribution systems, involving a central broadcasting system from which programs are distributed to local stations where the programs are amplified and reproduced; also for where the load is claimed, broadly, or by name only as a specific electrical art device, as for example, as a loudspeaker. (See Lines With Other Classes, G, "Amplifier Combined With Specific Source of Signal Energy," H, "Amplifiers Combined With Specific Load," and S, "Systems Utilizing Amplifiers," above.)
455, Telecommunications, 130 for radio receivers which may be limited to an amplifier and a detector; subclass 351 for portable radio receivers. (See Lines With Other Classes, S, "Systems Utilizing Amplifiers," above.)
455, Telecommunications, appropriate subclass, particularly subclass 335, where the same tube serves both as a detector and an amplifier. Class 455, subclass 342, includes combinations which comprise a reflex amplifier or subclasses 336+ for combinations which comprise a superregenerative detector. (Lines With Other Classes, P, "Amplifier and a Detector or Superheterodyne Converter and an Amplifier")
455, Telecommunications, 130 for a subcombination peculiar to radio receivers classified with radio receivers. (See Lines With Other Classes, P, "Amplifier And a Detector or Superheterodyne Converter And An Amplifier.")
505, Superconductor Technology: Apparatus, Material,
Process, 150 for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting device; and particularly subclass 180 for maser-type amplifying device, or subclasses 191+ for semiconductor device. (See Lines With Other Classes, R, "System or Devices Closely Related to or Analogous to Amplifiers, "S, "Systems Utilizing Amplifiers", and T, "Elements or Circuit Networks Commonly Used in Amplifiers,"above.)

GLOSSARY:
ACCEPTOR IMPURITY OR ACCEPTOR
A material which when added to a semiconductor material in minute quantities, as an impurity, induces hole conduction, generally causing the semiconductor to be one of "P-type conductivity".
ACTIVE NETWORK
A network containing a source of energy, or a sink of energy (i.e., a device for absorbing or dissipating energy other than that accounted for by the resistance of the components of the networks). Merely dissipating the heat generated by a resistance will not cause the resistance to be an active element. See Amplifying Device.
AMPLIFIER
Electric circuit means wherein a variable electrical current or voltage input signal is applied to an electrical amplifying device to control a source of electrical energy applied to the same device and from which is derived an output signal of substantially the same wave form as the input signal and substantially linearly related thereto.
AMPLIFIER CHANNEL OR CHANNEL
A part of an amplifier system in which a single signal path may be traced from a source to a load, and which path includes an amplifier as defined above. Such channel may be a cascade amplifier.
AMPLIFYING DEVICE
An electrical transducer of the active type wherein the electrical energy supplied by one system (power supply) is controlled by the electrical energy supplied by another system (signal source) limited to the active transducer device element itself such as a vacuum tube, transistor, controllable gas tube, saturable reactor, variable resistive element, etc.. See Active Elements.
AMPLITUDE LIMITER
A means in a circuit to limit the amplitude of the electrical voltage across it or the current in it to a value below or
above a fixed predetermined value, particularly the former.
ANODE
An electrode which acts as the positive terminal of an electric discharge or which acts as the positive terminal of an electric field to cause a discharge or accelerate the electrons in an electric discharge.
ATTENUATOR
Devices and networks consisting of one or more elements which exhibit only a positive resistance effect and which reduce the intensity of the energy passing through the device by dissipation, (1) the elements being proportioned to permit a change in their value to control the energy loss while maintaining substantially constant input and/or output impedance of the device, and/or (2) the elements being proportioned to permit the device to be inserted in the circuit to provide an energy loss without introducing any reflections in the circuit, and/or (3) the elements being combined with a long line or long line element, and/or (4) the device or network having an impedance equal to the impedance of a specified long line, and/or (5) the device or network is claimed as being particularly modified for use over a frequency band so that its characteristics are particularly related to frequency.
AUXILIARY GRID
Any grid, of an electronic tube other than the signal input grid.
BALANCED CIRCUIT
A circuit having its conductors electrically symmetrical with respect to a reference potential plane (e.g., ground). The potential between the two sides and ground are equal and of opposite sign. For example, a horizontal two-wire line may be a balanced line. See Push-Pull Stage.
BASE ELECTRODE
See the definition of point contact or junction transistor above.
BIAS, BIAS VOLTAGE, BIAS CURRENT
In an amplifying device, usually, a steady D.C.. voltage or current applied between two electrodes usually referred to the input electrodes to form an electric reference means for the control means, which influences the current flow of an electronic tube or semiconductor device or the flux relationships of a magnetic saturable reactor. See also Bias Control and Power Supply.
BIAS CONTROL
Control, as defined above applied to control of bias voltage or current of an amplifying device. This is distinguished from signal feedback in that the bias control voltage or current has a smoothed average value which adds to or subtracts from the bias voltage or current and is unlike the signal feedback voltage which varies instantaneously with the signal at the point from which it is derived. See also, Bias, Bias Voltage or Bias Current.
CASCADE AMPLIFIER
A series of amplifiers wherein the input for each amplifier except the first (to which the electric signal source is connected) is coupled from the output of the prior amplifier.
CATHODE OR CATHODE ELECTRODE
The negative electrode of the two electrodes of an electronic tube between which an electric discharge occurs (for negative charge carrier particles); in a vacuum tube the electrode which emits the electrons and is negatively charged with respect to the electrode which collects the electrons.
CATHODE-HEATER
A filament in proximity to an indirectly heated cathode with terminals designed to receive a source of power to heat the cathode to its electron emitting temperature.
CATHODE IMPEDANCE
The impedance from the cathode of an electronic tube to ground or a reference potential.
CHARGE CARRIER PARTICLE
A charged particle of matter involved in a flow of space current (electric discharge) and by means of which such current flows (current flow other than an electromagnetic wave propagated in open or confined space). Such charge carrier particles may be ions of a gas or charged atomic particles such as electrons.
COLLECTOR ELECTRODE
See the definition of point contact or junction type transistor below.
COMPRESSOR OR VOLUME COMPRESSOR
A device that compresses the volume range, as in recording sound, radio-telephone transmission, etc.. In compressing the signal volume range the amplification of large signals is reduced and of small signals is increased.
CONFIGURATION
The arrangement of electrodes of a transistor as input and output electrodes, e.g., common base configuration, where the base is included in both the input and output circuits of a transistor amplifier.
CONTROL
A selective adjustment of an element of an amplifier to vary the operation of the amplifier in a desired manner, or the characteristic of a part of the amplifier whereby in response directly to signal, or by means of a developed voltage or current in response to the signal, or by a voltage from some outside source, the impedance characteristics of a circuit element, or the electrical characteristics (bias or energizing voltage) of an amplifying device are automatically altered to change the operation of the amplifier in a predetermined manner. Such control may be by a nonlinear impedance element alone in a biasing or power supply circuit. The term control has not been applied in this class, when a nonlinear impedance element is in the signal path and affects the signal only, without any control from a separate path being applied to vary such impedance.
CONTROL ELECTRODE
An electrode designed to influence or control the discharge current flowing between other electrodes. It may depend for its effect on either its electrostatic effect or on the current flow thereto. The most common types of control electrodes are the signal control grid, or the gain control electrode or grid.
CONCENTRIC LINES
A transmission line in which one conductor extends within a second hollow conductor.
CONTROL GRID
A control electrode having grid construction.
D.C. COUPLING
A signal coupling network including a D.C.. conductive path. In a four terminal network such paths must be traced between terminals on the circuits to and from which the coupling is made which vary in voltage with the signal (this excludes D.C.. paths limited to ground leads or D.C.. shunt paths).
D.C. PATH OR D.C. CONDUCTIVE PATH
A path for current in a network which can conduct D.C.. current.
DELAY NETWORK
Networks including significant structure for retarding wave energy a predetermined period of time over a range of frequencies.
DIODE
Refers to any electronic tube, solid element, semiconductor, barrier layer device or other current carrier means limited to two electrodes and without additional magnetic or electrostatic means to influence the current flow, and which has marked unidirectional current characteristics.
DIRECTLY HEATED CATHODE OR FILAMENTARY CATHODE
A filament designed to have its terminals connected to a source of current, the filament being heated by the current passing through it and effective to emit electrons, designed to serve as a cathode of an electronic tube as defined above.
DISCHARGE PATH
The path of the free electrical charge carrier particles between the electrodes of an electronic tube.
DISTRIBUTED PARAMETER CHARACTERISTICS
A conductor or conductive means designed to operate at microwave or other high frequencies, so that the conductive means exhibits both distributed capacitance and distributed inductance at such frequencies.
DISTRIBUTED PARAMETERS
When the impedance of a transmission device or line at the operating frequency or band of frequencies is due primarily to the parameters of the device or line itself, and in considering the inductance, capacitance and resistance of the device or line they must be considered as mixed together and spread out along the device or line rather than being considered as in separate discrete lumps or devices as in the case of simple series and parallel circuits, the transmission device or line may be said to have distributed parameters. Examples of circuits with distributed parameters include telephone, telegraph and power lines for high frequency energy.
DONOR IMPURITY OR DONOR
A material which when added to a semiconductor in minute quantities, as an impurity, induces electron conduction, generally causing the semiconductor to become one of "N-type conductivity".
ELECTRIC CARRIERS OF A TRANSISTOR
Current flow in a transistor may be by negative carriers (electrons) or positive carriers (holes).
ELECTRIC DISCHARGE
The flow of current between two spaced electrodes at different potentials or the charge carrier particles conveying the current from one spaced electrode to the other.
ELECTRIC SIGNAL SOURCE OR SIGNAL SOURCE
The source of electrical signal energy to be amplified or the source of electrical signal energy which controls the electric power supply applied to the amplifying device.
ELECTRICAL CIRCUIT
An electrical network providing one or more closed paths.
ELECTRICAL NETWORK OR NETWORK
An arrangement of electrically connected electrical elements and/or devices which are capable of carrying electric A.C. or D.C.. current. Note. A network does not define the structure in space of the network elements or their arrangement in space relative to each other; it merely defines the elements or devices broadly by type as to the electrical function they perform and the electrical connections which will carry current between such elements and/or devices.
ELECTRODE
(1) In a vacuum tube, electronic tube or in any discharge device, the conductive elements between which the electric discharge takes place, and to which the power supply is applied; any additional conductive means placed in proximity to the electric discharge and/or other electrodes to affect electrostatically the discharge or the potentials of the electrodes with which they are in proximity. (2) In a magnetic amplifying device or in a resistive amplifying device, (including semiconductive devices) the terminals of windings which influence the operation of the magnetic device or the resistor or semiconductor terminals by means of which electric current may flow in or out of the resistor or semiconductor or by means of which a potential may be applied to the resistor or semiconductor.
ELECTROMECHANICAL TRANSDUCER
Means to convert the electric signal to mechanical vibrations and means further to convert the mechanical vibrations back to electric signals, such means generally serving as either time or phase delay means or means to determine the transmission frequency of the coupling network.
ELECTRONIC TUBE
An electric space discharge device, that is, a device in which electricity flows from one electrode to another by means of free electrical charge carrier particles traveling in a vacuum, gas or vapor; included are electric space discharge devices (also called electronic tubes) which operate in the open, i.e., not in an enclosed envelope. The electrical charge carrier particles may be of any type, usually electrons for vacuum tubes or charged ions for gas or vapor tubes.
EMITTER ELECTRODE
See the definition of point contact or junction type transistor in this Glossary.
EQUALIZER
Networks with attenuation or attenuation and phase distortion characteristics which vary over a frequency range for use in a wave transmission system for modifying the attenuation or attenuation and phase characteristics of the wave energy as a function of frequency.
EXPANDER OR VOLUME EXPANDER
A device that expands the volume range, as in recording sound, radio-telephone transmission, etc.. In expanding the signal volume range, the amplification of large signals is increased, and the amplification of small signals is reduced. Expanders are used generally to restore a signal after compression.
GRID
Is used in the conventional sense referring to the intended use and structure of the element in an electronic tube, particularly in a vacuum tube.
FILAMENT
A wire, ribbon, or rod conductive member.
FILTER
A frequency selective means.
FREQUENCY RESPONSIVE MEANS
Circuit means which acts on the signal to affect some frequency component of the signal differently from any other frequency components of the signal, for example, a tuned circuit or filter circuit which eliminates a frequency component, or an equalizer which emphasizes the signal amplitude of some frequency or frequency range of the signal with respect to others (e.g., tone control). See also,
Frequency Selective Means, below.
FREQUENCY SELECTIVE MEANS
Network means composed of some reactive elements which permit the passage of certain frequency components or a frequency component and block others. See also, Frequency Responsive Means.
GAIN
The ratio of the amplifier output power, voltage, or current to the amplifier input power, voltage or current.
GAIN CONTROL ELECTRODE
An electrode designed, together with the electron tube in which it is incorporated, to receive a D.C.. control voltage (other than the signal but which is usually derived from the signal), whereby changes in the control voltage change the gain of the tube.
GAS OR VAPOR TUBE
An electric discharge device which depends, for its operation, at least in part, upon ionization of a gas or vapor.
GRID OR GRID ELECTRODE
An electrode having one or more apertures therein, usually formed of open-work material such as wire mesh, etc.., and usually used as the signal or control electrode, or auxiliary electrode of an electron tube.
IMPEDANCE MATCHING NETWORK
Coupling networks which include one or more impedance elements construed or proportioned to substantially eliminate the reflected wave energy between the network and at least one of the connected circuits caused by impedance differences.
INDIRECTLY HEATED CATHODE (equiptential cathode)
A cathode designed to be heated to its emitting temperature by a separate heating element.
INPUT CIRCUIT OR COUPLING
The circuit or network of an amplifier extending from the source of electrical signal to the input electrodes of the amplifier, which may include the source of electrical signal.
INTERELECTRODE CAPACITANCE
The capacitive reactance for signal flow between any two electrodes of a vacuum tube, transistor or similar device inherent in their relationship to each other electrostatically and which for certain frequencies and voltages forms a path for the signal current usually detrimental to the operation of the circuit.
INTERELECTRODE IMPEDANCE
An impedance between electrodes of a vacuum tube, transistor, or similar device inherent in its structure, and manner and frequency of operation. This term is generic to inter-electrode capacitance above; and includes also input conductance caused by the transit time of electrons, etc..
INTERSTAGE CIRCUIT OR COUPLING
The electrical circuit or network by means of which the output signal from the output electrodes of the amplifying device of one stage of a cascaded amplifier is conveyed to the input electrodes of the amplifying device of the following stage of the cascade amplifier.
INTRINSIC CONDUCTIVITY
Refers to a semiconductor material which for a certain range of conditions has its free electron carriers and free hole carriers in approximate balance, so that the semiconductor material is neither N- nor P-type. Sufficient change in temperature or sufficient radiant energy impinging upon such a body will upset this equilibrium.
JUNCTION IN A TRANSISTOR OR SEMI-CONDUCTOR
The boundary of P-type and N-type semiconductor material.
JUNCTION TRANSISTOR
A transistor comprising two P-N Junctions back-to-back wherein a region of P- or N-type semiconductor material is common to both junctions (thus determining an NPN or a PNP junction transistor, respectively); an emitter electrode connected to one of the conductivity regions not common to the two junctions, normally forwardly biased (positive terminal of bias means to emitter for PNP type and negative terminal for NPN type); a collector electrode connected to the other conductivity region but common to the two junctions, reversely biased (negative terminal of bias means for the PNP type and positive terminal for the NPN type; and a base electrode connected to the region common to both junctions. See definition of Point Contact Transistor, which operates similarly in many respects.
LECHER LINES
A parallel transmission line with means to tune the parallel line.
LOAD
The electric device or circuit which utilizes the output signal derived from the amplifier after the input signal has controlled the electric power supply by means of the amplifying device to yield a signal which is a replica of the input signal but usually of greater amplitude.
LONG LINE
A wave transmission device or line having distributed parameters and especially designed to propagate electrical wave energy where the wave length of the transmitted energy is relatively short when compared with the length of the transmission line or device. The impedance of a long line is practically fixed by the constants of the line itself. The length of the transmission line or device may be a multiple or a fraction of a wave length, e.g., 1/4, 1/2, etc.., or otherwise have its length proportioned to the wave length of the energy with which it is to be used.
LONG LINE ELEMENT
A circuit element having distributed parameters, such as a resonator, or a wave guide. A long line element may be a part of a long line wave transmission device or used in a network with other circuit elements of the lumped parameter type, for example, as in the case of delay networks, impedance matching networks, wave filters.
LOOP PATH
In an amplifier having signal feedback, the path of the signal from the input point where the signal feedback is applied forward through the amplifier to the point in the circuit from which the signal feedback is derived through the signal feedback path to the aforesaid input point.
MAJORITY CARRIERS
See the definition of N- or P-type conductivity below.
MINORITY CARRIERS
See the definition of N- or P-type conductivity below.
NEGATIVE FEEDBACK
Signal feedback having at least some component thereof in opposite phase with the signal at the point where the signal feedback is applied.
N-TYPE CONDUCTIVITY
The characteristic of a semiconductor material, usually imparted by the addition of impurities of the "donor" type,
of an excess of free electrons over holes (free positive charges) at any time at room temperature, such negative charge carriers or electrons being referred to as majority carriers for current flow in such material, and holes as minority carriers for such current flow.
NEUTRALIZATION MEANS
Circuit means to eliminate, mitigate, or lessen undesirable effects of inter-electrode capacitance or inter-electrode impedance and which may include the input and/or output impedance of the amplifying device involved (such input or output impedance includes the inter-electrode impedance of the input or output electrodes).
NONLINEAR IMPEDANCE OR DEVICE
An impedance or device, which may be reactive or resistive or a combination of both and having the characteristic that for changes in voltage or current, the relationship of the voltage drop across the impedance or device, or the voltage applied across the impedance or device to the current flowing through it, is nonlinear.
OUTPUT CIRCUIT OR COUPLING
The circuit or network of an amplifier extending from the output electrodes of the amplifier to the load device, which may include the load.
PARASITIC REACTANCE, IMPEDANCE, CAPACITANCE, OR INDUCTANCE
Impedance characteristics of capacitive or inductive nature which are exhibited by conductive elements or conductive parts of a circuit at only high frequencies in a circuit designed for operation over a wide band and are inherent in the construction of such element or part. The presence of such reactances is undesirable and generally detrimental to the proper operation of the circuit. When a parasitic reactance is used as though it were a predetermined lumped reactance as in the case of the distributed capacitance of a coil being used to resonate therewith at a particular frequency; the distributed capacitance or other parasitic reactance is treated, for classification purposes, as though it were a predetermined lumped reactance in the circuit. Inter-electrode capacitances similarly involved in amplifiers as part of a tuned circuit are similarly treated.
PASSIVE NETWORK
A network containing no source of energy and in which no energy is dissipated other than that accounted for by the resistance of the components of the network.
PHASE SHIFT
Used to designate the change in phase relation between
voltage and current of the same wave energy, or between the voltages or the currents of different wave energy of the same frequency.
POSITIVE FEEDBACK
Signal feedback having at least some component thereof in phase with the signal at the point in the amplifier circuit where the signal feedback is applied.
POTENTIOMETER
A network which permits the division of a voltage applied across it, including adjustable means to select a particular division of the voltage applied across the network.
POWER SUPPLY
The source of electrical energy applied to an amplifying device which is controlled by the electric input signal. The term is used herein generically to include also a cathode heater supply, and bias voltage or current supply.
PLURAL AMPLIFIER CHANNELS
An amplifier system having at least two signal channels each containing separate amplifiers as defined above (wherein each amplifier may be a cascade amplifier), such amplifier channels may be completely separate from each other having separate and independent sources or loads; usually with some common control or they may be in parallel, having a common source and a common load; or the plural channels may be in branched circuits from separate sources or to separate loads.
POINT CONTACT TRANSISTOR
A transistor comprising a body of P- or N-type semiconductor material to which are attached two closely spaced electrodes connected at sharply defined points to the semiconductor material and a third electrode, the base relatively remote from the other electrodes and having a relatively large contact area (low resistance) for connection to the semiconductor. In this type of transistor the emitter is forwardly biased having, in N-type semiconductor material, the positive terminal of the biasing means connected to the emitter electrode, and for P-type semiconductor material the negative terminal of the biasing means connected to the emitter relative to the base, to inject minority carriers for the conductivity type semiconductor material (holes for N-type and electrons for the P-type) and the collector is biased reversely (having the negative terminal of the biasing means connected to the collector for N-type material and the positive terminal for P-type material), relative to the base so that minority carriers are collected there.
P-TYPE CONDUCTIVITY
The characteristic of a semiconductor material, usually imparted by "acceptor" type impurities therein, of an excess of free positive carriers (holes) over free negative carriers (electrons), such positive carriers or holes being referred to as majority carriers for current flow in such material and the electrons as minority carriers for such current flow.
PUSH-PULL STAGE
Includes two amplifiers each as defined above under "AMPLIFIER", the input electrodes of each of the amplifying devices of the two amplifiers being balanced to ground or some other convenient electrical reference plane, the source of electrical signal being such, and so coupled to the input electrodes, that at any instant the signal on each input electrode is substantially equal and opposite in sign to the signal on the other input electrode; and wherein the signal on the output electrodes of each of the amplifying devices is similarly balanced to a convenient electrical reference plane.
(1) Note. A balanced signal circuit is treated in this class as a special case of a single source or a single load. See Balanced Circuit.
(2) Note. A push-pull amplifier is treated in this class as a single channel, having a single source and a single load.
REACTIVE COUPLING
A coupling network including reactive means which may be inductive or capacitive.
RECTIFIER
A device with a unilateral current characteristic which permits the passage of only D.C.. current therethrough, and which is used to convert A.C. current applied thereto to D.C.. current.
RESONANT CIRCUIT
A circuit containing both inductive and capacitive reactance and in which the inductive reactance equals the capacitive reactance for a particular frequency. The resonant circuit may be series resonant, where the reactive elements are in series; or parallel (anti-resonant), where the inductive and capacitive elements are in parallel. See also, Resonator.
RESONATOR
Devices comprising conductive enclosures, cavities, or wave transmission line sections of the two terminal type, and having distributed inductance and capacitance, the line sections being terminated in other than the characteristic impedance of the line sections, the devices presenting
resonant characteristics to the existing source of wave energy. See also Resonant Circuit.
SATURABLE REACTOR
An inductive device having a core and at least one winding thereon in which the inductance is variable in accordance with magnetomotive force applied, up to a limiting value beyond which increased magnetomotive force does not change the inductance.
SCREEN GRID
A grid electrode placed between the control grid and the anode of a vacuum tube to reduce inter-electrode capacitance.
SECONDARY EMISSION ELECTRONIC OR VACUUM TUBE
A tube which depends for its operation, at least in part, upon the emission of electrons from a body due to collision of higher energy electrons with the body.
SECONDARY EMISSIVE ELECTRODE
An electrode which emits electrons upon collision with higher energy electrons. Since all electrodes have this characteristic, the term applies only to those electrodes designed to have an electron stream or beam impinge thereon to emit a stream or beam of secondary electrons.
SEMICONDUCTOR
A material having a specific resistance value of the order of that of germanium, silicon, selenium, etc.; or insulators whose specific resistance is reduced in value to the aforesaid range in operation, by alpha particle or electron bombardment or other means, so that the insulators operate broadly as semiconductors in an electrical circuit.
SEMICONDUCTOR AMPLIFYING DEVICE
An amplifying device constructed of a semiconductor with suitable electrodes for the application of signal current, power supply energy, and for the derivation of output signal current.
SIGNAL
A variable electrical current or voltage having characteristic variations in time, which characteristic variations are transmitted through an electrical network from a source in which the signal originates to a load where the signal is utilized.
SIGNAL ELECTRODE OR SIGNAL GRID
The electrode to which the signal is applied; in the case where such electrode is a grid electrode, the signal grid.
SIGNAL FEEDBACK
The application of a signal derived from an output electrode, to an input electrode of an amplifier or a prior stage of an amplifier. The input and output electrodes of the feedback may be the same or a common electrode as where vacuum tube space current flows through an unbypassed cathode impedance to change the potential on the cathode with respect to the control grid in accordance with the signal output. (For the distinction between signal feedback and bias control see the definition thereof, above).
SIGNAL FEEDBACK PATH
Circuit means to apply a portion of the electrical signal output of an amplifier to the input of the amplifier involving a shared impedance for the input and output circuits.
STABILIZATION MEANS
In an amplifier having a tendency to depart from a predetermined condition of operation, any circuit means used to maintain such predetermined condition of operation of the amplifier. See the definition of Control above.
STRUCTURE
Refers to any details of a circuit element as to the nature or composition of the material or materials of which it is made, the form or shape of the element or its parts or the relationship in space of such elements or parts or such characteristics of the elements relative to each other.
SWITCH
A device or means for opening or closing an electric circuit.
THERMALLY RESPONSIVE IMPEDANCE
An impedance element whose impedance value is responsive to the temperature changes therein by reason of the heat generated by the current flow therethrough, or the ambient temperature of the impedance element, or whose impedance value may be changed by separate electrical control means or other heat control means.
TRANSISTOR
An amplifying device comprising a semiconductor material to which contact is made by three or more electrodes.
UNBALANCED CIRCUIT
A circuit having its conductors electrically unsymmetrical with reference to a potential plane. For example, a concentric line is ordinarily unbalanced, the outer conductor being ordinarily connected to ground.
VACUUM TUBE
An enclosed space evacuated of most of its gas wherein an electric discharge takes place between two electrodes one of which emits electrically charged atomic particles, generally electrons and the other electrode collects such particles. The vacuum tube has at least one additional electrode or other means to control the flow of charged atomic particles between the emitter electrode and the collector electrode. The electric discharge of a vacuum tube is normally an electron discharge and any discharge of ionized particles is normally fortuitous and unintended. A vacuum tube is usually involved in a four terminal network, the input signal being supplied to two input electrodes usually the grid (control) and cathode (electron emitting electrode) and the output circuit normally being comprised of the power supply, the anode load impedance, the anode, the electron discharge, the cathode impedance, the load and the output coupling means. Thus the cathode which is normally present in the output and input circuits is normally the common electrode. Other alternative configurations where the input and output electrodes are not as above, as for example, where the anode is a common electrode and the cathode is the output electrode, are known and provided for in the schedule of this class. The terms for the grid, cathode and anode electrodes or auxiliary electrodes (as defined below) are referred to according to the predetermined use usually assigned for them regardless of the alternative circuit arrangements involved. The terms input, output, and common electrodes are used as in these definitions.
WAVE ENERGY
An undulatory disturbance propagated through a medium, (usually periodic in nature), its displacement varying periodically with respect to time or distance or both. The wave may be manifested in electrical, mechanical or acoustical form. However, in this class the term "wave energy" refers only to electrical wave energy.
WAVE GUIDE
A transmission device designed to propagate electrical waves having an electric or magnetic field component extending in the direction of propagation. The wave guide may be a hollow dielectric or metal tube, or a solid dielectric rod, the wave energy being propagated along the interior of the tube or rod and confined by the walls of the tube or rod.
WAVE TRANSMISSION DEVICE
Any device which is used to guide or constrain electrical wave energy and to convey the energy from one place to another. Included are conductors, wave guides, resonant structures (e.g., cavities, etc..).

This subclass is indented under the class definition. Subject matter wherein the amplifier is combined with other devices or structures having an added purpose or independent utility, other than to perfect the amplifier, and in which the utility of the art device is not destroyed by removal of the amplifier and which combination is not provided for elsewhere.
(1) Note. An example of art classifiable in this class and subclass is an amplifier combined with an automobile accelerator pedal to control the volume of the amplifier. The removal of the amplifier does not destroy the utility of the accelerator pedal (as it would in case of a radio receiver which included the amplifier or a part thereof).
(2) Note. Subject matter in which a source is claimed by name only as a specific art device, as for example, a microphone, is classified with the specific art device and not with amplifiers. Subject matter, in which the signal source device may be broadly claimed, not by name, but by some distinctive identifying feature thereof as, where a microphone source is claimed as a "means for converting sound signals", is not classified with amplifiers, but with the distinctive art device.
(3) Note. The terms generator or oscillator in claims, where they appear as sources of signal energy without further qualification except by their electrical characteristics such as impedance, reactance, etc.., are treated as generalized sources of signal energy and classification is with amplifiers except where specific details of the generator or oscillator are claimed; in such cases, classification is with the type of generator claimed or with oscillators in Class 331.
(4) Note. Where the load is claimed, even broadly, or by name only as a specific electrical art device, as for example, a loudspeaker, classification is not in this class, but with the load art device claimed. Where characteristics of the load device are claimed, which are peculiar to the disclosed electrical art device or to a specific type of electrical art device, classification is with the load art device established in the claim.
(5) Note. Subject matter wherein general electrical characteristics of the load are claimed, as for example, "a load having a variable impedance", is classified in this class.

This subclass is indented under the class definition. Subject matter involving means or methods of testing amplifiers as set forth in the class definition and/or amplifiers as set forth in the class definition combined with indicating means to show a condition of the amplifier.
(1) Note. Amplifiers combined with a meter or indicating means not involving a condition of the amplifier but where the amplifier is merely an instrument in facilitating such indication, are not classified in this class and subclass but in the appropriate subclass of Class 324, Electricity: Measuring and Testing or Class 340, Communications: Electrical, unless they are specialized for use in the testing of a specific electronic art device in which case, classification is generally with the specific electrical art device.

SEE OR SEARCH CLASS:
324, Electricity: Measuring and Testing, appropriate subclasses for electrical measuring and testing. See (1) Note, above.
340, Communications: Electrical, appropriate subclasses for systems with signal or alarm indicating means particularly 500. See (1) Note, above.

This subclass is indented under the class definition. Subject matter including at least two amplifying devices each of which is of a type different from the other.
(1) Note. When each of the amplifying devices is of a type which is classified in different subclasses of this class providing for such different types of amplifying devices, such as subclass 8 for saturable reactor type and subclass 44 for electron beam type, classification is in this subclass. Where the different types of amplifying devices are types provided for in coordinate subclasses indented under a major genus type, classification is not in this subclass, but in the appropriate subclasses indented under subclass 250.
Diverse type vacuum tube amplifying devices combined in an amplifier are classified in subclass 3 when each of the diverse type amplifying devices is of a type separately provided for by a subclass in this class, as for example, a traveling wave type amplifier classified in subclass 43 and an electron beam tube amplifying device classified in subclasses 44+. Where different types of vacuum tubes are involved, only one of which is provided for by a separate subclass, classification is not in subclass 3 but in the subclass providing for an amplifier having an amplifier device of that type. Combinations of vacuum tube and gaseous tube amplifiers are classified herein. Diode vacuum tube amplifiers combined with any other type of vacuum tube amplifier, whether provided for as a separate subclass or not, are classified herein.

SEE OR SEARCH THIS CLASS, SUBCLASS:
150 for cascaded vacuum tube amplifiers with amplifier devices having different characteristics (both amplifying devices being of the same general type).
299 for transistor amplifiers including combined diverse type semiconductors.
310 for plural cascaded stage transistor amplifiers including transistors having different characteristics.

This subclass is indented under the class definition. Subject matter wherein the amplifying device combines (1) a substance having the characteristic that certain molecular, atomic, or nuclear particles thereof are capable of excitation to a higher energy level; (2) means to raise such particles to the higher energy level state; (3) means for applying an electrical signal to the amplifying device; and (4) means for securing the amplified output therefrom, whereby the aforementioned excited particles in undergoing a change from the higher to a lower energy state emit radiation which is released by the applied electrical signal, thereby to amplify it.

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.
324, Electricity: Measuring and Testing, 300 for electrical measuring and testing means involving nuclear induction,
which refers to operation on a nuclear resonant principle similar to that employed in masers.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous circuits which may utilize a maser type circuit.
331, Oscillators, subclass 94.1 for oscillators of the molecular or particle resonant type, e.g., maser type.
332, Modulators, appropriate subclasses for modulators of the molecular or particle resonant type, e.g., maser type.
333, Wave Transmission Lines and Networks, subclass 24 for gyrator type wave transmission coupling means, including devices operating on a molecular or nuclear resonant principle similar to that employed in masers.
359, Optics: Systems (Including Communication) and Elements, 333 for optical or quasi-optical maser-type amplifying devices.

This subclass is indented under the class definition. Subject matter including (1) a nonlinear reactance, (2) means for applying an input signal frequency to said nonlinear reactance, (3) means for effectively applying a pumping frequency higher than said signal frequency to said nonlinear reactance, and (4) means for abstracting the amplified output therefrom, whereby sum and difference frequencies are produced, one or both of which (but usually the difference frequency {called the idler frequency} reacting with the pumping frequency to produce energy at the signal frequency which is combined in phase with the input signal.
(1) Note. While the pumping frequency is higher than the signal frequency, the pumping frequency may be derived from a lower frequency source, for example, as a harmonic of the lower frequency source.

SEE OR SEARCH THIS CLASS, SUBCLASS:
7 for an amplifier with a capacitive amplifying device.
8 for an amplifier with a saturable reactor type amplifying device.
53 for an amplifier with a distributed parameter coupling means.

This subclass is indented under subclass 4.5. Subject matter including structure for propagating energy of the various frequencies in interacting relationship with the nonlinear reactance.

SEE OR SEARCH THIS CLASS, SUBCLASS:
4 for maser type amplifying devices.
5 for solid element wave propagating devices generally.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnections Systems, subclass 424 for nonoptical parametric amplifier frequency converters, per se.
332, Modulators, 117 or 144+ for capacitive frequency or phase modulators, respectively, and subclass 173 for magnetic amplitude modulators.
333, Wave, Transmission Lines and Networks, 138, for delay networks.
359, Optics: Systems (Including Communication) and Elements, 326 for parametric optical frequency translators.
455, Telecommunications, 313 for receivers with frequency modification or conversion which may use parametric-type means; and subclass 336 for superrangenerative receivers.

This subclass is indented under subclass 4.6. Subject matter wherein the propagating structure is an electron beam device.

SEE OR SEARCH THIS CLASS, SUBCLASS:
43 for travelling wave amplifiers.

SEE OR SEARCH CLASS:
315, Electric Lamp and Discharge Devices: Systems, 3.5 and 39.3, for miscellaneous travelling wave tube systems.

This subclass is indented under subclass 4.5. Subject matter wherein the nonlinear reactance is of the gyromagnetic type.
(1) Note. The term "gyromagnetic" as applied to material designates magnetically polarized material (e.g., ferrites, garnets, and ionized gases) having unpaired spin systems which exhibit significant precessional motion in an orthogonal R.F. field.

SEE OR SEARCH THIS CLASS, SUBCLASS:
4.6 for travelling wave type amplifiers involving gyromagnetic nonlinear reactance.

SEE OR SEARCH CLASS:
333, Wave Transmission Lines and Networks, subclass 1.1 and 24.1+, for gyromagnetic plural channel systems and coupling networks respectively.

This subclass is indented under subclass 4.5. Subject matter wherein the nonlinear reactance is of the semiconductor type (e.g., a diode).

SEE OR SEARCH THIS CLASS, SUBCLASS:
4.6 for travelling wave type parametric amplifiers whose nonlinear reactance is of the semiconductor type.
250 for semiconductor amplifiers generally.

SEE OR SEARCH CLASS:
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous nonlinear circuits.

This subclass is indented under the class definition. Subject matter wherein the amplifying device comprises a solid-state element wave propagating means having associated means, such as a distributed parameter network, for coupling
a signal wave to be amplified to the wave propagating means.

SEE OR SEARCH THIS CLASS, SUBCLASS:
4 for amplifiers having amplifying devices of the maser type including those with solid element wave propagating means.
4.6 for travelling wave type parametric amplifiers which may utilize solid-state wave propagating means.
43 for traveling wave tube amplifiers.
45 for amplifiers having amplifier devices of the electron beam type which include an electrode coupled to a cavity resonator.
53 for amplifiers with distributed parameter type coupling.
250 for amplifiers having amplifying devices of the semiconductive type.

SEE OR SEARCH CLASS:
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous circuits which may include subject matter similar to the amplifiers classified in this subclass.
331, Oscillators, subclass 94.1 for oscillators of the laser type which may include solid element wave propagating means.
332, Modulators, appropriate subclasses for modulators of the laser type which may include solid element wave propagating means.
333, Wave Transmission Lines and Networks, appropriate subclasses, particularly subclass 24 for distributed parameter transmission coupling means including coupling means involving solid element wave propagating means.
372, Coherent Light Generators, appropriate subclasses for laser type oscillators.

This subclass is indented under subclass 5. Subject matter wherein the solid-state means is adapted to propagate and amplify signal waves in the form of acoustic, ultrasonic or hypersonic elastic waves of the phonon type.

SEE OR SEARCH CLASS:
181, Acoustics, subclass .5 for mechanical travelling wave
structures for propagating acoustic wave.
307, Electrical Transmission or Interconnection Systems, subclass 424 for nonoptical parametric amplifier frequency converters which may employ acoustic waves (e.g., Raman or Brillcuin devices).
310, Electrical Generator or Motor Structure, 311 piezoelectric devices in general which may propagate elastic waves of the phonon type.
333, Wave Transmission Lines and Networks, 138 for wave delay networks and subclasses 187+ for wave filters utilizing piezoelelectric wave propagating elements.
359, Optics: Systems (Including Communication) and Elements, 326 for parametric optical frequency translators.
367, Communications, Electrical: Acoustic Wave Systems and Devices, for compressional wave systems or transducers which may employ solid element wave propagating devices of the sonic or supersonic type.

This subclass is indented under the class definition. Subject matter wherein the amplifier includes means for applying or varying a magnetic field, and an electrical resistor subjected to such field or varying field in such manner that the value of the resistance transverse to the magnetic field changes, thus comprising a Hall Effect Device; such Hall Effect Device may comprise the amplifying device, per se, or may be included as a unilateralizing means (gyrator) to insure unilateral operation of the amplifier.

SEE OR SEARCH THIS CLASS, SUBCLASS:
8 for amplifiers having saturable reactor amplifying devices.
60 for amplifiers having magnetostrictive means in the amplifying device.
62 for amplifiers having a magnetoresistive type amplifying device.
63 for amplifiers having a magnetic means type amplifying device not elsewhere provided for.

SEE OR SEARCH CLASS:
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclass 511 for miscellaneous
circuits utilizing a Hall effect type element.
329, Demodulators, appropriate subclasses for demodulators including a Hall effect element.
333, Wave Transmission Lines and Networks, subclass 24 for Hall effect type gyrators, and subclasses 213+ for two terminal negative resistance networks.
338, Electrical Resistors, subclass 32 for electrical resistors whose resistance value changes in response to a magnetic field including resistors responding in accordance with the Hall effect.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is a nonlinear capacitor.
(1) Note. A nonlinear capacitor is one in which for any frequency, the ratio of the voltage across the capacitor to the current flowing through it, is not linear.
(2) Note. To be classified in this class the output signal must be a substantial replica of the input signal. Subject matter involving nonlinear capacitors in which the power supply, which is controlled by the signal, is A.C. must include filter means claimed to eliminate the A.C. power supply from the output signal or classification is in Class 307, Electrical Transmission or Interconnection Systems, subclasses 40+. However subject matter involving nonlinear capacitor amplifying devices wherein an A.C., power supply is used and claiming a demodulator will be classified herein even where the output filter is not claimed, if the filter is disclosed. It will be assumed to be part of the claimed demodulator.

SEE OR SEARCH THIS CLASS, SUBCLASS:
8 for amplifiers having saturable reactor type amplifying devices.
10 for amplifiers of the modulator-demodulator type.
86 for signal feedback amplifiers with variable impedance controlled by a separate path.
95 and 110, for signal feedback amplifiers with nonlinear impedance means.
143 for amplifiers having a thermally responsive impedance.
144 for amplifiers having a variable impedance for the signal channel controlled by a separate control path.
164 for amplifiers having an electronic tube or diode in an interstage coupling means.
174 for amplifiers having an electromechanical transducer (e.g., piezoelectric crystal) in an interstage coupling means.
183 for amplifiers having a nonlinear device in an interstage D.C.. coupling means.
250 for amplifiers having semiconductor type amplifying devices, particularly subclass 287.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, 401 for nonlinear reactor systems.
361, Electricity: Electrical Systems and Devices, 271 and 500+ for capacitors, per se.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is a saturable magnetic core with at least means to apply an electrical signal and an A.C. power supply to at least one winding thereon; the input signal which may be D.C.. or A.C. is applied to the signal winding to control an A.C. power supply applied to the power winding, which may be the same winding or a different winding.
(1) Note. To be classified in this class the signal output of the amplifier must be a substantial replica of the input signal. Therefore subject matter involving saturable reactors without filter means is not classified in this class with amplifiers, but is classified elsewhere. See the SEarch Class: notes below. Subject matter involving saturable reactors claiming a "demodulator" and disclosing a filter therewith but not claiming the filter are assumed to claim the filter as part of the demodulator and are classified herein.

SEE OR SEARCH THIS CLASS, SUBCLASS:
7 for amplifiers having capacitive type amplifying devices including "saturable capacitive reactor" means.
10 for modulator-demodulator type amplifiers.
60 for amplifiers having magnetostrictive means.
62 for amplifiers having magnetoresistive type amplifying devices.
63 for amplifiers having magnetic means amplifying devices.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, 416 for amplifiers using nonlinear reactors with a nonlinear output signal.
323, Electricity: Power Supply or Regulation Systems, subclass 249, 302, 310, and 329 for saturable inductive reactor circuits to control voltage magnitude. See (1) Note above.
336, Inductor Devices, 155 for the structure of saturable inductive regulators of the static type.
361, Electricity: Electrical Systems and Devices, subclass 204 for saturable reactors with electric relay or electromagnet load.

This subclass is indented under the class definition. Subject matter including a periodic switching means common to the input and output circuits of the amplifier.
(1) Note. This subclass includes essentially four types of subject matter containing a periodic switch, as follows:
(a) Where the signal is chopped to get A.C. which is fed to the amplifier and the amplifier output is chopped to get a D.C.. output (this subject matter is the same as is classified in subclass 10 below except that the modulator and demodulator are of the chopper type).
(b) The signal to the main amplifier is not chopped but a portion to another amplifier is combined with a signal from the output of the first amplifier and the two are chopped to get an A.C. signal which is used to develop a corrective signal for the main amplifier.
(c) The input is compared to the output by a periodic switch to develop a correction signal, generally for drift correction.
(d) The input and output signal are combined and then chopped and put into the main amplifier.

SEE OR SEARCH THIS CLASS, SUBCLASS:
83 for push-pull signal feedback amplifiers having a D.C.. feedback path.
97 for signal feedback amplifiers having a D.C.. feedback path.
121 for push-pull amplifiers having D.C.. interstage coupling.
125 for plural amplifiers having a D.C.. and an A.C. channel.
159 161, 163, and 181+, for D.C.. coupling involved in the interstage coupling.
187 and 191, for D.C.. input coupling.
194 and 198, for D.C.. output coupling.

This subclass is indented under the class definition. Subject matter including means for modulating the signal, which is usually D.C.. or low frequency A.C. amplifying means, and means to restore the original signal, eliminating any carrier frequency components.
(1) Note. The means for eliminating the carrier need not be specifically claimed to be classified in this class if such means are disclosed. As for example, where a demodulator is claimed alone, and a filter means to eliminate the carrier is disclosed the filter need not be claimed for classification herein. The claimed demodulator will be assumed to include the filter in such cases.
(2) Note. Where the modulator and demodulator are of the chopper type see the search notes below.
(3) Note. Including in the "means for modulating the signal" are chopper means to convert the signal to pulsating direct current or alternating current.

SEE OR SEARCH THIS CLASS, SUBCLASS:
7 for amplifiers having a capacitive type amplifying device including those which modulate and demodulate the signal.
8 for amplifiers having saturable reactor type amplifying devices including those which modulate and demodulate the signal.
9 for modulator and demodulator of the chopper type.

SEE OR SEARCH CLASS:
324, Electricity: Measuring and Testing, subclass 118, for measuring systems involving modulation-demodulation.
329, Demodulators, appropriate subclasses, for demodulator circuits.
332, Modulators, appropriate subclasses, for modulator circuits.

This subclass is indented under the class definition. Subject matter including means to restore a D.C.. component to the signal, usually by means of a D.C.. bias source and a rectifier circuit supplied to the control grid.

SEE OR SEARCH THIS CLASS, SUBCLASS:
140 for control of the input or gain control electrode including a rectifier in the bias circuit.

SEE OR SEARCH CLASS:
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 306 for miscellaneous circuits with amplitude control means.
348, Television, 691 for television systems including D.C. reinsertion circuits.

This subclass is indented under the class definition. Subject matter wherein the amplifying device includes electrodes in a gas or vapor medium and which device depends upon ionization of a gas or vapor for its operation.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, appropriate subclasses, particularly subclass 161, 163, and 567+ for gas or vapor tubes, per se.
315, Electric Lamp and Discharge Devices: Systems, appropriate subclasses, for circuits including gas or vapor
tubes as the ultimate load device.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous electronic tube circuits including gas or vapor tubes with a control electrode, controlled in operation.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is a vacuum tube including a secondary electron emissive electrode.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, 103, 377, 379, 399+, and 532+ for vacuum tubes, per se, having secondary emissive electrode.
315, Electric Lamp and Discharge Devices, Systems 5.11, 11, 12.1, 39.63 for circuits including vacuum tubes as load devices having a secondary emissive electrode.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is of the vacuum tube type including means for generating an electron stream or beam, and having additional means therein for propagating an electromagnetic wave or component thereof at a velocity reduced from the free space velocity of the wave and propagated in proximity of the electron stream or beam, permitting exchange of energy between the electrons and the electromagnetic wave.

SEE OR SEARCH THIS CLASS, SUBCLASS:
5 for amplifiers having a solid element wave propagating amplifying device.

SEE OR SEARCH CLASS:
315, Electric Lamp and Discharge Devices, Systems, 3.5 and 39.3 for traveling wave type tubes involved as the load device in miscellaneous circuits. See the search notes under subclasses 3.5 and 39.3.
331, Oscillators, subclass 82 for traveling wave tube type oscillators.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is a vacuum tube provided with means to form the electric space discharge into a restricted beam or ray, usually pencil-like.
(1) Note. Means to control the electron trajectory of the electrons emitted from the cathode (as in magnetrons which are classified below) is not regarded as an electron beam forming means required for classification in this and indented subclasses.
(2) Note. Subject matter broadly claiming so-called "beam power tubes" are not classified in this subclass but are classified below in the appropriate subclass for the circuit involved.

SEE OR SEARCH THIS CLASS, SUBCLASS:
42 for amplifiers having secondary electron emission tube amplifying devices.
43 for amplifiers having traveling wave type amplifying devices.
47 for magnetrons.
308 for amplifiers including an electron beam forming means and a semiconductor element as a target means therein.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, 364 for cathode-ray tubes, per se. See the search notes of Class 313.
315, Electric Lamp and Discharge Devices: Systems, 1 for cathode- ray tubes with means to supply electric current or potential thereto and/or cathode ray tubes structurally combined with a circuit element. See the search notes of Class 315.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclass 600 for miscellaneous circuits having a particular beam tube structure.
329, Demodulators, appropriate subclasses and particularly subclass 368 for an amplitude demodulator employing an electron discharge device of three or more electrodes.

This subclass is indented under subclass 44. Subject matter wherein at least one electrode is coupled to a cavity resonator.

SEE OR SEARCH THIS CLASS, SUBCLASS:
49 for amplifiers having vacuum tube amplifying devices with distributed parameter characteristics.
56 for amplifiers with cavity resonator coupling means generally.

SEE OR SEARCH CLASS:
331, Oscillators, subclass 83 for multicavity beam tube (Klystron) oscillators.

This subclass is indented under subclass 44. Subject matter including means to deflect the electron beam.

SEE OR SEARCH THIS CLASS, SUBCLASS:
41 for amplifiers having gas or vapor tube amplifying devices including those having means to deflect the ionized gas or vapor stream.
65 for amplifiers including vacuum tube amplifying devices having distinctive structural characteristics or specific structural details not elsewhere provided for in the schedule.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, 421 for cathode-ray tubes, per se, having electron stream or beam deflecting means.
315, Electric Lamp and Discharge Devices: Systems, 364 for cathode- ray tubes with means for deflecting the cathode ray.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is of the vacuum tube type including means for magnetically influencing the electric discharge in the device, and not provided for above.

SEE OR SEARCH THIS CLASS, SUBCLASS:
41 for amplifiers having a gas or vapor type amplifying device including those with magnetic means to deflect the ionized stream of gas or vapor particles.
42 for amplifiers having secondary emission tube amplifying devices including those with magnetic means.
43 for traveling wave type tube amplifiers which may include magnetic means.
44 for electron beam tube amplifying devices which may include magnetic means.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, 153 for discharge device combined with a magnetic device. See the Notes and search notes of Class 313.
315, Electric Lamp and Discharge Devices: Systems, 39.51 for magnetrons. See the Notes and search Notes and search Notes of Class 315.
329, Demodulators, subclass 322 for a magnetron type frequency modulator and subclass 354 for a magnetron type amplitude modulator.
331, Oscillators, 86 for magnetron oscillators.

This subclass is indented under subclass 47. Subject matter wherein the input signal is coupled to the means for magnetically influencing the electric discharge.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is of the vacuum tube type and includes within the vacuum tube an electrode or
other element having distributed parameter impedance characteristics.
(1) Note. Distributed parameter characteristics as used in the definition above include long lines and long line elements such as lecher lines, parallel transmission lines in general, concentric lines, wave guides, cavity resonators, tuned transmission lines, etc.., which possess distributed capacitance and inductance. For the definition of such means, see the class definition for Class 333, Wave Transmission Lines and Networks. Inherent capacity or inductance as for example between electrodes or of a lead inside the tube when made use of as a lumped reactance circuit element is classified in the appropriate subclass involving the circuit; neutralization by feedback is classified in subclasses 76+ below.

SEE OR SEARCH THIS CLASS, SUBCLASS:
4 for amplifiers having a maser type amplifying device which may include distributed parameter impedance structure.
5 for amplifiers having a solid element wave propagating amplifier device.
43 for amplifiers including traveling wave tubes.
45 for amplifiers of the type having an electron beam tube amplifying device with an electrode coupled to a cavity resonator.
53 for amplifiers with distributed parameter type coupling. See the search notes thereunder.

SEE OR SEARCH CLASS:
315, Electric Lamp and Discharge Devices: Systems, 39 for a vacuum tube combined with distributed parameter type transmission means structure, with the tube as the load device. See the notes and search notes thereunder.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclass 593 for miscellaneous circuits with distributed parameters.
359, Optics: Systems (Including Communication) and Elements, 333 for laser amplifiers.

This subclass is indented under the class definition. Subject matter including in addition to the amplifying device of the vacuum tube type, a similar vacuum tube, with the
cathode unheated, so that the additional tube does not serve as an active element but merely presents impedance relations in the circuit similar to those of the amplifying device vacuum tube, usually for neutralizing the effects of the amplifying device interelectrode impedances.

SEE OR SEARCH THIS CLASS, SUBCLASS:
76 for amplifiers having signal feedback means to compensate for inter-electrode impedance. See the notes and search notes thereunder.

This subclass is indented under the class definition. Subject matter combined with switch means, which may be of the electromechanical or electronic tube type (vacuum, gas, or vapor tubes), to disable or discontinue the operation of the amplifier automatically in response to a predetermined condition.
(1) Note. Miscellaneous gating circuits are classified in Class 327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclasses 365+ unless significant details of an amplifier as classified in the class definition of this class are claimed when classification is in this class.

SEE OR SEARCH THIS CLASS, SUBCLASS:
65 for specific structure involved in the amplifier including structure involving switching means.
127 for amplifiers having means to control power supply or bias voltage.

SEE OR SEARCH CLASS:
200, Electricity: Circuit Makers and Breakers, appropriate subclasses, for switches, per se.
307, Electrical Transmission or Interconnection Systems, 112 for electrical transmission or interconnection switching systems.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 365 for miscellaneous gating circuits.
361, Electricity: Electrical Systems and Devices, 1 for electrical systems and devices with safety and protection means including those involving disabling switching means; subclasses 139+ for circuits for electric relays.

This subclass is indented under the class definition. Subject matter including means for control of the amplifier which may be for control of the bias of an amplifier device electrode or of a variable impedance for the signal channel, wherein the signal input includes a component of a particular frequency not involved in the signal for signal purpose, which is selected by a means in or associated with the amplifier and applied to the control means or used to develop a control voltage applied to the control means.
(1) Note. See the class definition, Lines With Other Classes and Within This Class, for other systems utilizing pilot frequency control.

SEE OR SEARCH THIS CLASS, SUBCLASS:
85 for signal feedback amplifiers having an amplifier in the feedback path.
86 for signal feedback amplifiers having a variable impedance in the feedback path controlled by a separate control path.
96 for signal feedback amplifiers combined with control of bias of the signal amplifier.
127 appropriate subclasses, for control of bias or power supply, particularly subclasses 130 and 132. See the search notes under subclass 127. See also (2) Note under subclass 130.
143 for amplifiers having a thermally responsive impedance which may be controlled by a separate means.
144 for amplifiers having a variable impedance which may be controlled by a separate control path.

SEE OR SEARCH CLASS:
333, Wave Transmission Lines and Networks, appropriate subclasses for pilot current controlled transmission line systems, generally. See the note and search notes.
370, Multiplex Communications, subclass 491 and 500 for a multiplexing system using pilot control.

This subclass is indented under the class definition. Subject matter wherein the signal energy is coupled to or from the amplifying device by means including distributed parameter wave transmission means; or circuit networks of lumped parameters or impedances designed to simulate the impedance characteristics of distributed parameter wave transmission means.
(1) Note. Distributed parameter transmission means as used in the definition above include long lines and long line elements such as telephone and telegraph lines, lecher lines, parallel transmission lines, in general, concentric lines, wave guides, cavity resonators, tuned transmission lines, etc.., which possess distributed capacitance and inductance. For the definition of such means and "lumped parameter or impedance" means as used above, see the class definition for Class 333, Wave Transmission Lines and Networks. Subject matter involving inherent capacity or inductance, as for example, between electrodes, or of a lead inside a tube when made use of as a lumped reactance circuit element, is classified in the appropriate subclass involving the circuit. Neutralization by feedback is classified in subclasses 76+ below.
(2) Note. Subject matter including distributed parameter circuit coupling means when combined with a special type of amplifying device is classified with the special type of device and not in this subclass. For example, subclass 43, for amplifiers having traveling wave type tubes, which include distributed parameter type delay lines, or wave guides.

SEE OR SEARCH THIS CLASS, SUBCLASS:
3 for amplifiers having plural diverse type amplifying devices.
4 for amplifiers having a maser type amplifying device.
5 for amplifiers which have solid element wave propagating amplifying devices.
43 for amplifiers having a traveling wave type tube amplifying device.
45 for electron beam tube amplifying devices coupled to a cavity resonator.
49 for amplifiers having an amplifying device of the vacuum tube type having distributed parameter characteristics.
107 for signal feedback amplifiers having phase shift means in the loop path.
157 for amplifier interstage coupling.
185 for amplifier input coupling.
192 for amplifier output coupling.

SEE OR SEARCH CLASS:
315, Electric Lamp and Discharge Devices: Systems, appropriate subclasses indented under subclass 3 and subclass 39 for distributed parameter impedance devices.
333, Wave Transmission Lines and Networks, appropriate subclasses for passive distributed impedance devices. See the notes under the class definitions and search notes under the pertinent subclasses of Class 333.

This subclass is indented under subclass 53. Subject matter wherein a plurality of amplifier devices are in a system having a single source and load, include a delay line coupling (which may be a distributed parameter line, or an artificial line) and wherein the inputs or outputs of such amplifier devices are coupled to such delay line means at phase displaced points.
(1) Note. Push-pull amplifiers including delay line coupling, per se, are not classified in this subclass but in subclass 55 below.

SEE OR SEARCH THIS CLASS, SUBCLASS:
124 for plural channel amplifiers. See the notes and search notes thereunder.

This subclass is indented under subclass 53. Subject matter including at least one push-pull stage of amplification.
(1) Note. A push-pull stage of amplification for this class requires a balanced input to two tubes and a balanced output therefrom; for further details of the definition of a push-pull stage of amplification see the class definitions of this class, section I.

SEE OR SEARCH THIS CLASS, SUBCLASS:
118 for push-pull amplifiers generally. See the notes and
search notes thereunder.

This subclass is indented under subclass 53. Subject matter wherein the distributed parameter wave transmission means is of the wave guide, cavity concentric line type and is resonant.

SEE OR SEARCH THIS CLASS, SUBCLASS:
45 for electron beam tube amplifying device coupled to a cavity resonator.
94 and 109, for signal feedback amplifiers having frequency responsive means in the feedback path.
302 for semiconductor amplifiers having frequency responsive in the signal transmission path.

SEE OR SEARCH CLASS:
331, Oscillators, subclass 83 for multicavity beam tube oscillators (Klystrons).
333, Wave Transmission Lines and Networks, 219 for distributed parameter type resonators. See the note and search notes to this subclass.

This subclass is indented under subclass 53. Subject matter wherein there is included as a signal coupling means a circuit network of lumped parameters or impedances, which is designed to simulate the impedance characteristics of a distributed parameter wave transmission means.
(1) Note. Distributed parameter transmission means as used in the definition above include long lines and long line elements such as telephone and telegraph lines, lecher lines, parallel transmission lines, in general, concentric lines, wave guides, cavity resonators, tuned transmission lines, etc.., which possess distributed capacitance and inductance. For the definition of such means and "lumped parameter or impedance" means as used above, see the class definition for Class 333, Wave Transmission Lines and Networks. Subject matter involving inherent capacity or inductance, as for example, between electrodes, or of a lead inside a tube when made use of as a lumped reactance circuit element, is
classified in the appropriate subclass involving the circuit. Neutralization by feedback is classified in subclasses 76+ below.

SEE OR SEARCH CLASS:
333, Wave Transmission Lines and Networks, subclass 23, for passive type artificial line, per se; and subclasses 138+, for delay lines.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is provided with a rotating dynamoelectric means; and wherein the power supply electrical energy source which is controlled, may be developed by conversion of mechanical energy to electrical energy by the motion of the armature of the dynamoelectric means, the signal current being applied to magnetic field means of the device, so that a current is generated which varies with the signal current supplied; or the rotating dynamoelectric means may act as a motor with the signal current applied to the rotating means or the field means, and the rotary motion of the device may be utilized as a variable resistor means to effect a control of the power supply source.
(1) Note. Subject matter, as defined above, is classified herein where the device is disclosed as designed to amplify a signal. Where the system is primarily for the conversion of electrical energy into mechanical energy or vice versa, or is of general utility, classification is in Class 310, Electrical Generator or Motor Structure, or Class 322, Electricity: Single Generator Systems, as described in the, SEARCH CLASS, below. Where the structure of a dynamoelectric machine is claimed, alone, classification is in the appropriate subclass of Class 310, Electrical Generator or Motor Structure.

SEE OR SEARCH CLASS:
310, Electrical Generator or Motor Structure, 10 and subclasses indented thereunder for the structure of dynamoelectric machines, per se, especially indented subclasses 139 and 151 for the structure of generators of the rotary amplifier type.
322, Electricity: Single Generator Systems, appropriate subclasses particularly subclass 61 for generators with alternating current excitation and subclasses 90 and 91+ for rotating amplifiers, especially indented subclass 92 for such amplifiers of the crossed-field type.

This subclass is indented under the class definition. Subject matter including means controlled by light or activated by light which may be involved in the amplifying device, per se, used as a control means, or which may be included in any other part of the amplifier.
(1) Note. Subject matter wherein light controlled or activated means is not a part of the amplifier but is combined therewith (as for example, as a photo-electric cell with light means therein feeding a signal current to a vacuum tube amplifier) is not classified in this class.

SEE OR SEARCH THIS CLASS, SUBCLASS:
308 for amplifiers having atomic particle or radiant energy impinging on a semiconductor amplifying device. See the search notes thereunder.

SEE OR SEARCH CLASS:
250, Radiant Energy, 200, appropriate subclasses for photocell circuits. See also the notes and search notes under subclass 200.

This subclass is indented under the class definition. Subject matter wherein the amplifying device includes magnetostrictive means, that is, means for cyclically changing the dimensions of a body of magnetic material under the influence of a cyclically changing magnetic field in proximity to the body of magnetic material.

SEE OR SEARCH THIS CLASS, SUBCLASS:
174 for interstage coupling including electromechanical transducer means (e.g., piezoelectric crystals). See the search notes thereunder.

SEE OR SEARCH CLASS:
333, Wave Transmission Lines and Networks, 148 and 186+ for electromechanical transducer delay lines and filters, respectively. See the search notes thereunder.
336, Inductor Devices, subclass 20 for inductive devices having magnetostrictive (deformable) cores.

This subclass is indented under the class definition. Subject matter wherein the amplifying device, to which the electric input signal is applied to control the power supply source of electric energy also applied thereto, is a resistive means, which may be liquid, solid, or of granular construction.
(1) Note. Not included herein, are other devices having resistive properties such as gas tubes, vacuum tubes, etc..
(2) Note. Variable resistors, although including a sensing means and/or power supply means, as structure are classified in Class 338, Electrical Resistors. Where such subject matter involves a load circuit, classification is herein, when the signal output is "substantially a replica of the signal input"; otherwise classification is in the appropriate subclass of Class 323, Electricity: Power Supply or Regulation Systems.

SEE OR SEARCH THIS CLASS, SUBCLASS:
250 for amplifiers with semiconductor type amplifying devices. See the notes and search notes thereunder.

SEE OR SEARCH CLASS:
323, Electricity: Power Supply or Regulation Systems.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for systems utilizing variable resistance devices of the nonlinear conductor type and which systems are not elsewhere classifiable.
338, Electrical Resistors, appropriate subclasses for the structure of resistors, per se, especially subclass 100. See (1) Note above.

This subclass is indented under subclass 61. Subject matter wherein the amplifying device resistive means is of a type whose resistance value varies in response to a magnetic field or a change in magnetic field, and includes means for applying such magnetic field to the resistive means.

SEE OR SEARCH THIS CLASS, SUBCLASS:
6 for amplifiers having Hall Effect type amplifying devices.
60 for amplifiers having magnetostrictive means.
63 for amplifiers having an amplifying device with magnetic means, generally.

SEE OR SEARCH CLASS:
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclass 511 for miscellaneous circuits using the Hall effect.
338, Electrical Resistors, subclass 32 for electrical resistors whose resistance value changes in response to a magnetic field or a change in magnetic field.

This subclass is indented under the class definition. Subject matter wherein the amplifying device includes a magnetic means to control the power supply energy or is involved in the structure of the amplifying device in some other manner and which is not provided for above.

SEE OR SEARCH THIS CLASS, SUBCLASS:
6 for amplifiers including Hall effect type amplifying devices.
41 for amplifiers including gaseous or vapor type amplifying devices which may have magnetic means for deflection or other purposes.
44 for amplifiers having electron beam tube amplifying devices which may have magnetic means for beam deflection, focusing or other purposes.
47 for amplifiers having magnetically influenced discharge devices including magnetrons.
60 for amplifiers having magnetostrictive means.
62 for amplifiers having magnetoresistive type amplifying devices.

This subclass is indented under the class definition. Subject matter wherein the amplifying device is of the vacuum tube type having a positively charged grid (with respect to the cathode) immediately adjacent the cathode, which neutralizes the negative space charge of the electrons emitted from the cathode so that a "virtual cathode" is produced on the side of the space charge grid on which the anode is situated, said tube having a normally negatively biased control grid next to the space charge grid, to which the signal is coupled, and an anode to receive the electrons emitted by the cathode, and which may have additional electrodes between the control grid and the anode.

SEE OR SEARCH THIS CLASS, SUBCLASS:
65 for amplifiers including vacuum tubes of special structural characteristics.
199 for power or bias voltage supply for amplifiers, see the search notes thereunder.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, appropriate subclasses, for discharge device structure, per se.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 524 for miscellaneous electron tube circuits with space charge grid tubes.
329, Demodulators, subclass 368 for an amplitude demodulator using an electron discharge device of three or more electrodes.

This subclass is indented under the class definition. Subject matter involving the structure of any amplifier circuit element, such as resistors, vacuum tubes, etc.., with the exception of the structure of transformer elements, or of the structural relationships of such elements in the amplifier.
(1) Note. The term structure, herein, refers to the arrangement in space of the parts to the whole of the circuit element or of the elements comprising the amplifier which includes also the material of which such parts are constructed. The term structure is distinguished from circuit or circuit arrangement in that the latter refers to an abstract schematic of parts identified broadly by their function in the circuit and arranged according to the
sequence of signal current flow and not according to actual arrangement in space, or construction.
(2) Note. Subject matter involving the structure of transformers is not classified in this or indented subclasses but in subclasses 171, 190, or 197 below.
(3) Note. Subject matter involving the structure of any amplifying device or associated therewith, of the types specifically provided for above are not classified in this or indented subclasses but in the appropriate subclasses for those types, above.

SEE OR SEARCH THIS CLASS, SUBCLASS:
53 for amplifiers having distributed parameter coupling means including the structure of such distributed parameter means.

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, for the structure of electrical insulators and conductors.
200, Electricity: Circuit Makers and Breakers, for the structure of switches and circuit breakers.
313, Electric Lamp and Discharge Devices, appropriate subclasses for the structure of electric discharge devices (vacuum tubes and gas tubes), per se.
315, Electric Lamp and Discharge Devices: Systems, 3 for combined cathode-ray tube and circuit element structure, subclasses 32+ for vacuum or gas tubes combined with integral circuit structure or temperature modifying means structure where the tube is the load device.
334, Tuners, appropriate subclasses for tuners, per se.
336, Inductor Devices, appropriate subclasses for inductor structure.
338, Electrical Resistors, for the structure of resistors and rheostats.
361, Electricity: Electrical Systems and Devices, 271 for capacitor structure, subclasses 600+ for housing and mounting assemblies with plural diverse electrical components, subclasses 679+ for electronic systems and devices, and subclasses 500+ for electrolytic capacitors.
439, Electrical Connectors, appropriate subclasses for the structure of electrical connectors.
455, Telecommunications, 130 for radio receiver structure in general; and subclass 351 for portable radio receivers.

This subclass is indented under subclass 65. Subject matter wherein the capacitive electrode structure, inductor structure, resistors, conductors, connectors and/or related circuit elements form a conductive coating on a base. For example, such as is produced by printing, spraying, electro-deposition or similar coating method, or by the removal of adherent conducting material from an insulating base by etching, grinding, or the like.

SEE OR SEARCH CLASS:
174, Electricity: conductors and Insulators, 250 for preformed panel circuit arrangement (e.g., printed circuits).
336, Inductor Devices, subclass 200 for inductor coil structure of the printed circuit type. See the search notes thereunder.
361, Electricity: Electrical Systems and Devices, 736 and 748+ for printed circuits of the type used in radios.
439, Electrical Connectors, 55 for connectors of the preformed panel circuit (e.g., printed circuit) type.

This subclass is indented under subclass 65. Subject matter wherein the structure involved is that of a capacitor or capacitive element of the amplifier circuit.

SEE OR SEARCH THIS CLASS, SUBCLASS:
157 appropriate subclasses thereunder for interstage coupling circuits involving capacitors.
185 appropriate subclasses for input coupling circuits involving capacitors.
192 appropriate subclasses for output coupling circuits involvi