We found this circuit in an Electronic Design. The main integrated circuit is the 4017. The frequencies are determined by the RC circuits as well as the duration of the generated pulse train.
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...