Here is the 2SC5242 documentation as a 173 KB PDF, placed in the schematic category but evidently a part datasheet going by its name. Under JIS rules the 2SC designation identifies an NPN bipolar transistor. The larger file size hints at characteristic curves and package drawings, though the name itself says nothing more. Use it to check voltage, current and power ratings, pinout and thermal limits. That lets you choose a correct replacement, or judge whether a measured junction reading is normal.
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.