This circuit was found in a 1968 General Electric manual. The circuit is for 3 A motors but can be changed according to the SCR used. The SCR is type 106 and R1 is 10k.
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...