Definition

(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 microphonewhich 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 inappropriate 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.