A 69.5 KB PDF for the 3SK248, catalogued as a schematic and most likely a manufacturer datasheet for the part. Only the type number is stated. Japanese JIS numbering assigns 3SK to four-terminal N-channel FETs, a class mostly consisting of dual-gate MOSFETs used in RF stages of radios and TV tuners. Consult it for gate 1, gate 2, source and drain identification, maximum ratings and package outline, and keep static precautions in mind when removing or fitting the device.
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.