This circuit makes use of an integrated LM2907. The circuit is from an old documentation being applied to cars that still used platinum, common at the time.
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...