The 2SC5098 transistor is the only identifier in this 298 KB PDF, which the index files under schematics. Since JEITA reserves the 2SC prefix for NPN bipolar transistors, it is in all likelihood the device datasheet, covering limits, gain, frequency or switching behaviour and mechanical data. The name carries no maker, revision or application. Before substituting, compare voltage, current, dissipation and package with the original, and confirm the lead arrangement shown in the drawing against the board footprint.
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.