Compact 65.7 KB PDF for the 2SK2539, listed as a schematic but named after a discrete semiconductor. Japanese JIS designations use 2SK for N-channel field-effect transistors. No maker, package or edition appears in the file name. Technicians consult a sheet like this to locate the gate, drain and source leads, read the maximum ratings and confirm suitability of a replacement in a switching or amplifier circuit. Check the actual part marking first, since similar numbers can differ greatly.
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.