This circuit was found in Radio Electronics magazine from October 1964. The circuit uses two transistors of the time that require a supply voltage of 9 V. Consumption is 2.5 mA.
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...