This circuit was suggested by Sprague Electric in an 80's documentation. The circuit uses a tachometric sensor for feedback. The current was not indicated in the original documentation.
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...