Component sheet for the 2SC3644 in a 120 KB PDF. JIS designation rules assign 2SC to NPN bipolar transistors; no device, board or version is mentioned in the name. Though catalogued as a schematic, it is probably a datasheet with maximum ratings, hFE ranges and a mechanical drawing. Use it to identify base, collector and emitter, to check the part suits the voltages present in the circuit and to choose an equivalent with a matching package and 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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)