This circuit from a 1970s General Electric publication applies to motors of the series winding type. SCRs support current equivalents and must be equipped with heat sinks.
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...