The 2SC4688 transistor is documented in this 178 KB PDF, which the catalogue files under schematics. In the JIS convention, 2SC means an NPN bipolar transistor, and the name contains no suffix or further detail. A technician reads it to find terminal order and package style before removal, and to obtain the maximum ratings used when testing or selecting a substitute. Open it in any PDF viewer and verify the code on the board part, since neighbouring numbers such as 2SC4689 are different devices.
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.