This circuit was found in a 1964 documentation. It shows how to achieve automatic gain control for an oscillator. The transistors are of the time and the circuit controls signals from 2.6 to 3.1 kHz.
With the circuit shown, we have an excellent level for the signal obtained from an electret...
We found this circuit in a 1960 Sylvania transistor manual. The relay can be 12 V and C1...
This circuit is from a Popular Electronics from 1992. The circuit employs an equivalent transistor and...