This circuit with current up to 100 mA according to the transformer was found in the Radio Electronics magazine of October 1991. The regulation is done directly by the zeners.
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...