Editing Opto-isolator (section)

==Operation==
An opto-isolator contains a source (emitter) of light, almost always a [[infrared|near infrared]] [[light-emitting diode]] (LED), that converts electrical input signal into light, a closed optical channel (also called dielectrical channel<ref name=M100/>), and a [[photodetector|photosensor]], which detects incoming light and either generates electric [[energy]] directly, or [[modulation|modulates]] [[electric current]] flowing from an external power supply. The sensor can be a [[photoresistor]], a [[photodiode]], a [[phototransistor]], a [[silicon-controlled rectifier]] (SCR) or a [[TRIAC|triac]]. Since LEDs can sense light in addition to emitting it, construction of symmetrical, bidirectional opto-isolators is possible. An optocoupled [[solid-state relay]] contains a photodiode opto-isolator which drives a power switch, usually a complementary pair of [[MOSFET]]s. A [[slotted optical switch]] contains a source of light and a sensor, but its optical channel is open, allowing [[modulation]] of light by external objects obstructing the path of light or reflecting light into the sensor.