Covering the 2SC4306, this 100 KB PDF is indexed as a schematic, but with no board or device named it is best treated as the transistor datasheet. The JIS 2SC designation marks an NPN bipolar part, usually stamped C4306. Technicians consult such sheets to map the pins of the specific package, check collector-emitter breakdown voltage and current limits, and review gain grades, then confirm junction health with a diode test before ordering a matching or equivalent part.
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.