We found this circuit in a Radio Electronics from October 1963. The circuit uses an output transformer with a center tap. The trimpot is adjusted for higher gain and lower quiescent current.
This circuit was found in American documentation from 1966, but it can be assembled with a modern...
This circuit consists of a bistable touch switch with the known CMOS 4013 double flip-flop. The...
This bistable and monostable Vox circuit was found in a 2002 documentation. The 556 is a double 555...