Found in 1967 documentation, this circuit makes use of period transistors and drives a common light bulb. Nothing against it being adapted to use LED.
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...