Found in a 1966 Electronics World, this circuit applies to the protection of any analog instrument. The diodes can be of any general-purpose type.
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...