This shield circuit with an optical coupler was found in an 90s EDN. The circuit can be used with voltages from 0 to 600 V with the indicated component values.
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...