Оптроны

Optocoupler is the electronic device that consists of a light emitter (usually - LED or miniature incandescent lamp (in older models)) and a photodetector (bipolar or field phototransistors, photodiodes, photothyristors, photoresists) that are associated in one optical channel and manufactured in the same case. Operation principle is to convert electrical signal into light signal, transmit it trough the optical channel and convert this signal back to the electrical on the exit.