We found this circuit in a 70s Electronic Design documentation. The circuit uses general-purpose transistors from the time. Linearity is better than 0.25%.
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...