This device enables you to turn a circuit on and off optically. It consists of a moulded plastic housing with an IR LED facing a phototransistor across a gap. Any object in the gap will interrupt the IR beam and consequently switch the phototransistor on and off.The device is very fast and ideal for counting, timing or sensing.Full specs supplied with each unit.FEATURES:- PCB or chassis mounting - Low cost- Rugged one piece construction - Very fast