PDF datasheet of 96.4 KB for the 2SA1641 transistor, with no manufacturer or revision given in the name. JIS numbering assigns the 2SA prefix to PNP bipolar transistors intended for high-frequency circuits. At the bench it helps identify base, collector and emitter, confirm the package fits the footprint, and compare ratings and gain classes against possible substitutes. Since markings usually omit the 2S, the part on the board will typically read A1641. Any PDF reader will open the file.
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.