Datasheet for the 2SD662 NPN transistor, stored as a 44 KB PDF; the _E ending likely marks an English version of the document. JIS numbering assigns the 2SD prefix to NPN transistors designed for low-frequency work. A repair technician uses such a sheet to read pinout drawings, maximum ratings, electrical characteristics and package details when testing a suspected short or open junction and when picking an equivalent part. Compare footprint and lead arrangement with the board before installing any replacement.
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.