This circuit shows how to interface a CMOS circuit with a microcontroller or other circuit using an optical coupler. The load is normally a 1k resistor and the circuit output is at the collector of the phototransistor. The supply (2) is 5 V for microcontrollers and for CMOS depends on the application. The difference with the previous circuit (CB18263E) is that the output is activated at the low level.
