Found in an old Popular Electronics this circuit is still current. The SCR can be of the 106 series and the relay according to the voltage used in the supply. The voltage can be 12 V.
Using the CA3140 in the figure we have a comparator that goes low in the window voltage space. The...
With this circuit it is possible to connect a comparator to a power stage via two wires. The...
This simple circuit was found in the May 1979 issue of Radio Electronics magazine. The circuit has the...