Identified solely as 2SJ257, this 96.0 KB PDF most likely documents a P-channel FET, the device class assigned the 2SJ prefix in the JIS system. It appears in the schematic section, but with no model or board in its name it is best treated as a datasheet. Technicians reach for such a file to read off pin functions, voltage and current ratings, thermal limits and package outline. A normal PDF viewer is enough. Match the printed marking and footprint of the original before selecting an equivalent part.
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.