This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be replaced by a TIP42 mounted on a heat radiator.
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...