Covering the 2SC5028, this 219 KB PDF is filed as a schematic yet is named like a component datasheet. The 2SC prefix belongs to the JIS scheme and designates an NPN bipolar transistor. The name holds no other information about manufacturer, package or application. Technicians consult such sheets for pin identification, maximum ratings and characteristic curves, which help when checking a suspect part out of circuit or picking a substitute with equal or higher limits. Verify the part marking on the PCB before trusting the data.
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.