Found in American documentation from the 1990s, this circuit has active cycle control. The basic components are given along with the diagram. Transistors are general purpose.
Found in a 90s Popular Electronics, this circuit triggers a load from the audio signal applied to...
This old receiver (1967) uses germanium transistors from the time and coupling transformers,...
I found this circuit in a Popular Electronics from 1992. The circuit can be easily implemented with BC549...