This circuit was found in an Electronics Now from the 90's. The integrated regulator circuit and the power transistor must be equipped with heat radiators.
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
This power source with silicon diodes at a time when valves were still used was found in Radio...