English-language edition, judging by the _E suffix, of a document for the 2SB1488 transistor, stored as a 46 KB PDF under schematics but almost certainly a datasheet. The JIS prefix 2SB marks a PNP transistor for low-frequency applications. A compact file like this usually holds ratings, characteristics and an outline drawing. Repair technicians consult it to confirm base, collector and emitter positions, check voltage and current limits, and qualify a replacement before soldering it onto the board.
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.