This circuit was found in the April 1970 Radio Electronics magazine. The dual function circuit uses 4 transistors and is connected to the vehicle's contact breaker.
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...