(under the class definition) Subject matter involving significant detail or distinctive characteristics of the electrical circuit coupling a source of signal energy to the input of the amplifying device; or involving electrical characteristics of the source; or involving input electrical parameters of the amplifying device to which the signal input is coupled.
(1) 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 specific art device and not with amplifiers. Subject matter in which the source device may be broadly claimed, not by name, but by some distinctive identifying feature thereof, as where the microphone source is claimed as a "means for converting sound signals", classification is not with amplifiers but with the distinctive art device.
(2) Note. The term "generator" or "oscillator" in claims, where either appears as a source of signal energy without further qualification except an electrical characteristic such as impedance, reactance etc.., is treated as a generalized source of signal energy, and classification is with amplifiers. Where specific details of the generator or oscillator are claimed, classification is with the type of generator established in the claims or with oscillators in Class 331, Oscillators.
(3) Note. Amplifier subject matter disclosing an interstage coupling but wherein only the input coupling to the succeeding stage is claimed and no interstage coupling or details to establish such coupling are claimed, is not classified in this and indented subclasses. See the search this class, subclass notes below for Interstage Coupling.
SEE OR SEARCH THIS CLASS, SUBCLASS:
65+, for input coupling involving structure of any of the input circuit elements.
74, for plural inputs to series energized tubes. 106, for amplifiers having feedback in series with the input source.
108, for input coupling which may include a potentiometer therein common to the signal and feedback paths.
116, for amplifiers with balanced input involved in balanced-to-unbalanced circuits.
117, for amplifiers with unbalanced input involved in unbalanced-to-balanced circuits.
122, for push-pull amplifiers with significant input coupling.
143, for amplifiers having thermally responsive impedance which may be in the input coupling.
144, for amplifiers with variable impedance controlled by separate control path which may be in the input coupling.
147, for plural signal inputs.
157+, appropriate subclasses for input coupling involved in interstage coupling particularly subclasses 158+ and 160+. See (3) Note under this subclass above.
192, for output coupling networks.
252+, for semiconductor amplifiers with plural inputs. 275, and 301, for semiconductor amplifier devices having balanced coupling.
SEE OR SEARCH CLASS
333, Wave Transmission Lines and Networks,
24+, for passive coupling networks for wave transmission generally.
338, Electrical Resistors, appropriate subclasses for the structure of rheostats or resistors which may be used in input coupling.
