This post explains for the semiconductor MOC7811.
The Part Number is MOC7811.
The function of this semiconductor is (MOC78xx) Couplers / Interrupters.
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Slotted couplers consist of an infrared emitting diode facing a photodetector in a molded plastic housing. A slot in the housing between the emitter and the detector provides a means of interrupting the signal. A wide selection of standard and custom housings and detector fuctions is available.
Motorola offers high performance Infrared Emitters and Detectors for fiber optic systems.
Other data sheets are available within the file: MOC7812, MOC7813 MOC7821, MOC7822, MOC7823