This precision signal rectifier was obtained in an American technical documentation from 1975. The operational amplifiers can be 741 and the power must be supplied from a symmetrical source.
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...