This classic windscreen wiper interval setup was found in American documentation from the 90s. The circuit can be found with variations at other points on this site.
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...