The signals from this circuit obtained from the 1965 Radio Shack documentation are picked up from a medium wave receiver. L1 and L2 have 80 to 100 turns of yarn 28 on a ferrite rod.
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...