Catalogued as a schematic, the 243 KB PDF titled 2SC5109 gives no device or board context, so treat it as a component datasheet. Japanese JIS numbering assigns the 2SC prefix to NPN bipolar transistors, and the case typically reads C5109. Open it in any PDF reader to check pin assignment and outline dimensions, then compare maximum voltage, current, power dissipation and frequency parameters against the circuit requirements before replacing a suspect part with an equivalent.
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.