Indexed under schematics, the 116 KB PDF named 2SC5155 refers to a discrete semiconductor rather than a whole board. In JIS numbering, 2SC identifies an NPN bipolar transistor meant for high-frequency circuits, so this is likely its datasheet. No other information appears in the name. Use it to read the pinout diagram and package drawing, absolute maximum ratings and electrical characteristics, which helps when diode-mode testing a suspect part or selecting a replacement with equal or better specifications.
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.