The circuit is from a June 1995 Electronics Now. The relay is power-dependent and both R1 and R2 should have close resistances in operation.
We found this circuit in a year 2000 documentation. It must be powered by a voltage of 5 V as it...
This circuit was found in the February 1990 issue of Radio Electronics magazine. The circuit uses...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...