This circuit was obtained in a 1980s publication, but it can be easily assembled today, as all components are common. The transformer is 12 + 12 V with at least 1 A and the diodes 1N4002.
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...