(under the class definition) Subject matter in which the "source of electrical energy" controlled by the signal input; or biasing means applied to the "amplifying device", or the means to apply such energy or bias, such as the circuits through which such source or bias is applied; or means for isolating such source or biasing means from the signal path or other amplifier circuits (by filters, isolating resistors, or other means), is significantly claimed, and which subject matter is not provided for in any of the previous subclasses.
(1) Note. Merely claiming power supply source or biasing means by name only or broadly without significant detail or distinctive characteristics is insufficient for classification in this and indented subclasses.
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4, for maser type amplifying devices.
5, for solid element wave propagating amplifying devices.
6, for Hall effect type means.
7, for capacitive amplifying devices. 8, for saturable reactor type amplifying devices.
41, for gas or vapor tube amplifying devices.
42, for secondary electron emission tube amplifying device.
43, for traveling wave type tube.
44+, for electron beam tube amplifying device.
47+, for magnetically influenced discharge devices, (e.g., magnetrons).
49, for vacuum tube having distributed parameter impedance characteristics.
58, for rotating dynamoelectric amplifying devices.
60, for magnetostrictive type amplifying devices.
61+, for restrictive and magnetoresistive type amplifying devices.
63, for significant power supply or biasing means combined with an amplifying device and magnetic means which controls the energy of said power supply or biasing means, or when a magnetic means is involved in some other manner in the structure of an amplifying device combined with significant power supply or biasing means. 64, for space charge grid tubes biased to operate as such.
70+, for series energized vacuum tube amplifiers and 18 for series energized semiconductor amplifiers.
113, for polyphase power supply.
114+, for unrectified A.C. power supply.
123, for amplifiers including a push-pull stage having significant bias or power supply means.
127+, for amplifiers with means to control the bias or power supply voltage.
142, for cathode self-biasing circuits.
149, for hum elimination by introduction of the hum component in the signal path in opposed phase.
296, and 297, for semi-conductor type amplifying devices when combined with significant power supply or bias means or involving related circuitry.
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307, Electrical Transmission or Interconnection Systems,
149+, for miscellaneous "power pack'' systems. 315, Electric Lamp and Discharge Devices: Systems,
91+, for cathode or cathode heater including anode supply circuit but not including any grid biasing circuit.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,
530+, for miscellaneous circuits combined with power supply or bias means.
329, Demodulators, appropriate subclasses for demodulators with particular power supply.
359, Optics: Systems (Including Communication) and Elements,
