PDF reference for the 6N135 and 6N136, 86 KB, catalogued under schematics. These part numbers belong to a common family of high-speed optocouplers, so the document is a component datasheet rather than a full board diagram. Repair technicians use it to confirm the pinout, isolation circuit and current transfer figures when checking feedback or signal isolation stages. Read the part marking carefully, since the two numbers have different ratings and look-alike parts may not be drop-in replacements.
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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.