Compact 25.2 KB PDF named for the 3SK301, categorised as a schematic but most likely a part datasheet. Nothing besides the type number appears in the name. JIS designation 3SK covers N-channel FETs with four leads, commonly dual-gate MOSFETs used in VHF and UHF amplifier and mixer circuits. Consult it for terminal layout, package drawing and electrical limits, and make sure any cross-reference part matches both the ratings and the footprint before installing it.
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.