This circuit, which can use the 4011 or 4001, was found in documentation from the 90s. The load depends on the transistor used, and the power supply must be isolated.
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...