Abstract: An AC input signal and a DC supply voltage are applied to a tapped coil having end points from which differential input signals are coupled to a differential variolosser that controls the gain of cascaded differential amplifiers. The two output terminals of the cascaded amplifiers are electrically connected together through a pair of equal valued resistors to provide a DC reference voltage at the junction of the two resistors, where the AC signals cancel. The reference voltage is coupled to one side of a high-gain differential control amplifier and to both sides of a differential half-wave rectifier circuit. One side of the rectifier is also connected to one output of the cascaded amplifiers for detecting an amplified signal there. The detected signal is integrated and coupled to the other side of the control amplifier to produce the control signal which regulates the drive current to and loss presented by the variolosser, and thus the level of the input signals to the cascaded amplifiers.

Abstract: Gain control circuits in the base and emitter circuits of a common-emitter transistor amplifier stage each include pluralities of resistors and electrically conductive screw-type switches which are connected together such that the net changes in decibel values of gain provided by closing individual switches are cumulative. Resistors in the emitter gain control circuit are electrically connected in parallel with the emitter resistor in the AC equivalent of the amplifier in various configurations by closing screw switches to decrease the effective emitter resistance and thereby increase the decibel value of amplifier gain in steps of prescribed magnitudes. The switches are selectively closed in a prescribed manner to provide step changes in the decibel value of the net gain of the stage in discrete consecutive steps of the same magnitude. Transistor amplifiers with emitter gain control circuits may be connected in series to provide additional steps and range of voltage gain.

Abstract: Gain control circuits associated with the base and emitter electrodes of a common-emitter transistor amplifier stage include pluralities of electrically conductive screw-type switches and resistors. The net gains provided by the associated gain control circuits are cumulative and determine the net gain of the stage. The gain changes provided by individual switches of the base and emitter gain control circuits are also cumulative, the switches being selectively closed in a prescribed manner to provide step changes in the decibel value of the net gain of the stage in discrete steps of the same magnitude. A plurality of transistor amplifiers with associated emitter gain control circuits may be connected in series, with the decibel values of voltage gains thereof also being additive, to provide additional steps and range of voltage gain. Series resistors in the base gain control circuit are selectively short-circuited by screw switches to decrease the input resistance of the amplifier stage.