This circuit is from an old English publication from 1968. We can implement it with TIP32 transistors in a more modern version. Power can be done with either large batteries or a power supply.
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...