This audio-driven relay was published in the July 1977 issue of Radio Electronics magazine. The circuit uses CMOS components, and the relay must be a sensitive type.
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...