Abstract: The amplification of periodic or aperiodic pulses is varied by envelope detecting the received pulses and passing the resulting envelope waveform to a latching comparator which, when enabled, provides an output pulse whenever the input waveform has an amplitude which exceeds a predetermined value. An itegrator coupled to the output of the comparator is continuously operative to increase or decrease the gain of the amplifier according to the absence or presence respectively of the output comparator pulse. In this manner the amplitude of signals or pulses is automatically controlled despite circuit and transmission vagaries.