A 171 KB PDF for the 4N39 and 4N40 optocouplers, listed under schematics but in practice a component datasheet. These parts are optically coupled isolators with a thyristor-type output, intended for switching AC loads from logic circuits. Expect pin assignment, LED trigger current, blocking voltage and isolation ratings. The document helps when checking a failed isolator in a control or power board and confirming that a replacement matches the output type, since phototransistor optocouplers are not drop-in substitutes.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.