The 2SC4935 is covered by this 176 KB PDF, filed as a schematic but, judging by the bare JIS part number, almost certainly the transistor datasheet. Under JIS numbering the 2SC prefix identifies an NPN bipolar transistor. Expect characteristic curves, ratings tables and package dimensions. A technician relies on these figures to verify a suspect part with a meter in diode mode, pick a suitable substitute and confirm thermal limits. Match the printed code on the component before using the pin assignment shown.
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.