The 2SD2179 transistor is the subject of this 43.9 KB PDF, carrying an _E suffix in its name. JIS convention assigns the 2SD prefix to NPN bipolar transistors for low-frequency service, so the content is most likely a datasheet despite the schematic label. No maker, package or variant is named. When a board has a shorted or open transistor, a sheet like this confirms the pinout and ratings, letting you test the part properly and pick a replacement with equal or better voltage and current limits.
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.