This circuit was found in a 1974 publication. It consists of a voltmeter for high voltages, up to more than 100 V, using a neon lamp.
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...