Specification PDF, 30.2 KB, for the 2SC3913 transistor. JIS part numbering assigns the 2SC prefix to NPN bipolar devices, so the document is most likely a datasheet listing pin functions, absolute maximums, electrical characteristics and package outline. No other detail is stated in the name. For repairs it supports in-circuit diagnosis of a dead or leaky transistor and helps select a replacement with equal or better ratings. Confirm the marking and package on the PCB before relying on the pinout.
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.