This sensitive circuit was found in an Electronics Hobbyists Handbook from the 1990s. The circuit can use common general-purpose transistors in place of the original ones.
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...