Found in an RF Design from the 90s, this circuit is based on components from the time. It can, however, be implemented with equivalent modern components.
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...