Datasheet-type PDF for the 2SC3912, sized at 30.2 KB. The part number follows the JIS standard, where 2SC identifies an NPN bipolar transistor; the name offers no package, maker or application details. Inside one expects ratings, characteristic curves and dimension drawings. A technician uses them to identify terminals, verify that a substitute part tolerates the same voltages and dissipation, and interpret meter readings across junctions. Compare the board marking with this number before replacing anything.
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.