Specification sheet for the 2SD874 transistor in PDF form, about 44 KB, catalogued with the schematics but actually a component datasheet. The 2SD prefix places it in the JIS family of NPN low-frequency transistors. Inside you can expect maximum ratings, electrical characteristics, gain classification and package drawings, which help when measuring junctions with a multimeter or cross-referencing a substitute. The trailing E in the file name probably refers to the document edition or language; check package type against the part fitted.
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.