This circuit was obtained in a documentation from the 80's. However, using TTL it is still modern, being able to be used as Shields for microcontrollers or part of digital projects.
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...