This circuit serves as an audio output for AM or even FM radios and was found in a Radio Electronics magazine from March 1990. Note the supply voltages.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...