Abstract: Signal level control for an amplifier or the like is provided by a binary counter which counts upward when first operated, and which thereafter counts up and down if continually operated. If the operated counter is stopped after counting up, it counts up when operated again. If the operated counter is stopped after counting down, it counts up when operated again. A digital to analog converter can provide a single control signal from the counter. The user is always assured that the single control signal will increase when the counter is operated again following a prior operation in either direction.

Abstract: An amplifier is provided with two transistors connected as a differential amplifier having an emitter current source. Input signals are applied to one transistor and output signals are derived from the other transistor. These output signals are applied to an output transistor also connected as a current source that is one-half the emitter current source of the differential amplifier. This provides a steady state output voltage from the output transistor that can be set at a desired level to provide symmetrical limiting.