This amplifier with gain control was obtained in a documentation from Signetics of the 80's. Transistors are of power and operational amplifiers are not common nowadays.
This RS flip-flop uses two type 4N26 optical couplers and is characterized by the very high...
Found in July 1975, Radio Electronics magazine this circuit can use any operating circuit,...
We found this circuit in an old American publication. The transistors can be BC558 and diode 1N34....