We found this circuit in an article in Radio Electronics magazine from November 1971. The circuit has several sensor inputs and is based on programmable unijunction transistors or PUTs.
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...