This post explains for the semiconductor MOC7811.
The Part Number is MOC7811.
The function of this semiconductor is (MOC78xx) Couplers / Interrupters.
Manufacturers : Motorola
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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 within the file : MOC7812, MOC7813 MOC7821, MOC7822, MOC7823