(under the class definition) Subject matter wherein there is provided for the signal transmission path a variable impedance element or circuit which may be a variable resistance, or reactance, whose impedance is controlled by a separate control means.
(1) Note. Examples of control of variable impedances classified in this and indented subclasses are; a control voltage secured from the signal output which may be rectified, filtered and applied to a biased diode or to the control electrode of an electronic tube to vary its impedance, or to control an electric motor which may vary a potentiometer or adjustable reactance in the signal path.
(2) Note. Considering the signal coupling means as a four terminal network the "variable impedance" of the subclass may be in series between corresponding terminals or in shunt across the signal transmission path.
SEE OR SEARCH THIS CLASS, SUBCLASS:
52, for amplifiers having pilot frequency control means.
70+, for series energized vacuum tube amplifiers.
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 varied by a separate control path.
95, and 110, for signal feedback amplifiers having a nonlinear impedance in the feedback path.
96, for signal feedback amplifiers having means to control the amplifier bias voltage.
108, for potentiometer common to signal and feedback paths.
127+, for amplifiers having control of power supply or bias voltage, particularly subclasses 138, 139, and 140.
143, for thermally responsive impedance in the signal path including those varied by a voltage or other means from a separate control path.
155, for amplifiers having unicontrol coupling.
164, for cascaded amplifiers having an electronic tube or diode in an interstage coupling circuit.
174, for cascaded amplifiers having an electromechanical transducer (e.g., piezo-electric crystal) in an interstage coupling path.
183, for cascaded amplifiers having a nonlinear device in a D.C.. interstage coupling.
185+, for variable impedance in amplifier input networks. 192+, for variable impedance in amplifier output networks.
293, and 296, for series energized semiconductor amplifiers.
299+, for combined diverse type semiconductors where one may be a variable impedance for the signal transmission path.
SEE OR SEARCH CLASS
323, Electricity: Power Supply or Regulation Systems,
234, 289 for transformer and impedance systems for voltage magnitude control.
324, Electricity: Measuring and Testing
98, 99+, and 101 for electrical measuring and testing circuits having bridges with variable impedances thereon, which are varied by a separate control means.
333, Wave Transmission Lines and Networks, appropriate subclasses particularly
14, 15, 16, 17.1+, 81, and 213+ for wave transmission systems with variable impedance in the wave transmission path.
334, Tuners, appropriate subclasses for tuners, per se.
336, Inductor Devices, appropriate subclasses for the structure of variable inductors. 338, Electrical Resistors, appropriate subclasses for the structure of variable resistance devices.
