Using the 555 and 7400 this circuit was found in the September 1977 Radio Electronics magazine. The power supply must be made with a voltage of 5 V.
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...