Catalogued as a schematic, this 184 KB PDF is named only after the part number 2SC5175, so it is most likely the manufacturer datasheet for that discrete transistor. Under the Japanese JIS scheme, a 2SC prefix marks an NPN bipolar transistor intended for high-frequency use. Technicians open such sheets in any PDF reader to confirm pinout, package, maximum ratings and marking codes before fitting a replacement. Check the body marking on the board against the document, since tiny SMD parts often carry abbreviated codes.
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.