This stage was found in a 1964 Electronic Design. The transistors are of the time and the shape of the signal obtained is shown in the diagram.
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...