This circuit is from a 1978 magazine Radio & Electronics Constructor, but it can be assembled with 1N4004 diodes and TIC106 SCRs for motors up to 1A. The transformer has a secondary 12 V x 1 A.
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...