This interesting multi-channel circuit was found in the August 1988 issue of Radio Electronics magazine. It monitors the signal from 4 sound channels simultaneously.
This circuit needs only 0.7 V at 40 uA to drive the relay. We found it in the November 1993...
Found in a 1964 Electronic Design this circuit makes use of components of the era. The output is 2 V...
The circuit shown in the figure shuts off a load when the voltage drops below the value determined...