The 2SK2171 referenced in this 180 KB PDF is an N-channel field-effect transistor by JIS/EIAJ convention, which uses the 2SK prefix for that class. The file is filed as a schematic, but a bare part number like this normally indicates a datasheet. Maker and package are not in the name. Consult it for lead identification and maximum ratings, and use its electrical characteristics to judge whether a substitute part is suitable 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.