This circuit was obtained in an Electronics World of 1968. The operational amplifiers ones are types of the time, no longer used today. The circuit responds from less than 20 Hz.
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...