This circuit triggers a relay when a light beam that hits the phototransistor is cut off. The circuit is from Electronics Now and the supply voltage depends on the relay voltage.
This shield circuit can serve as a basis for a digital mixer or simply for a switch without noise...
This shield or interface makes it possible to control power loads connected to the power grid from...
Based on an LM36000 OTA this circuit was found in the July 1988 issue of Radio Electronics...