The amplifier drives the base of a common emitter PNP MPS6517 operating with a voltage gain of about 20. RL control varies the quiescent point of the transistor Q, so that varying amounts of signal exceed the level of V r, diode D 1 rectifies the positive peaks Ql output is only when these peaks are more larger than r V `'` 7. 0 volts. The result is filtered ex Rx. s, controls the charging time constant or time of attack. Cx is involved in two loading and unloading. R2 (150 K, the input resistance of the emitter-follower Q2) controls the decay time.
Making the disintegration of long and short of attack is accomplished by small and large Rx R2. (An emitter follower Darlington may be necessary if the extremely slow decay times are required.) The emitter-follower Q2 drives the AGC Pin 2 of the MC1590 and reduces the gain. R3 controls the slope of signal compression.