The 2SC4861 datasheet appears to be what this 117 KB PDF contains, although it is filed in the schematic category. Only the part number is stated. Under JIS/JEITA rules a 2SC code marks an NPN bipolar transistor. Technicians open such a file to read absolute maximum ratings, gain and frequency characteristics, and the pin assignment of the package. Knowing the pin order is essential before diode-mode testing, and the ratings guide the choice of a safe substitute when the original is unavailable.
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.