Here the subject is the 2SD2167, delivered as a 51.2 KB PDF filed as a schematic. By JIS convention the 2SD prefix belongs to NPN bipolar transistors for low-frequency applications, so the content is most probably a component datasheet. The name gives no manufacturer, package or version. Useful for checking which lead is base, collector or emitter, reading maximum ratings and gain bins, and verifying that any replacement can handle the voltage and current in the circuit being repaired.
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.