The optocoupler relay consists of two parts: the photoelectric input part and the relay output part.

The photoelectric input part includes light emitting diodes (LEDs) and phototransistors (photoresistors or photodiodes). The light emitted by the LED illuminates the photosensitive element, generating current.

The output part of the relay is controlled by the current of the photosensitive element through a transistor or transistor, which controls the operation of the relay and isolates the input signal from one circuit to another. This isolation can be used for signal transmission, noise isolation, and other applications.