Opto Coupler
Opto coupler is a solid state component in which light
emitter the light path and light detector are all enclosed within the component
and cannot be altered externally. Usually infrared emitting diode (IRED) can be
used as a light emitter. Photo transistor can be used as a light detector.
Principle:
Here is one way transistor of electrical signal from LED
(IRED) to photo transistor without any electrical connection between the input
and output circuitry.