(under subclass 144) Subject matter wherein the variable impedance means is an electron tube, either vacuum tube or gaseous which has a control means effective during operation of the tube, or a diode.
SEE OR SEARCH THIS CLASS, SUBCLASS:
70+, for series energized vacuum tube amplifying devices.
85, for signal feedback amplifiers having an amplifier in the feedback path.
138, 139 and 140, for amplifiers having means to control the input electrode bias voltage including respectively, biased rectifiers or discharge devices, electronic tube, or rectifier in the bias control circuit.
164, for cascaded amplifiers having an electronic tube or diode in the interstage coupling circuit.
185+, for amplifier input coupling networks which may have an electronic tube or diode as an impedance therein. 192+, for amplifier output coupling networks which may have an electronic tube or diode impedance therein.
299+, for combined diverse type semiconductors where one of the semiconductors may be a diode or transistor impedance for the signal transmission path.
SEE OR SEARCH CLASS
323, Electricity: Power Supply or Regulation Systems,
227, and 291 for discharge devices on voltage magnitude control systems generally.
333, Wave Transmission Lines and Networks,
213+, for negative resistance and/or reactance networks of the active element type.
334, Tuners,
14+, for a tuner unit in which a reactance tube is used.
