The diagram shows a tone control with the LM381 IC. The circuit is from a Radio Electronics from February 1990. The power supply is simple.
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...