A 32.8 KB PDF for the 3SK273, indexed as a schematic though it is likely a manufacturer datasheet. JIS naming assigns 3SK to four-lead N-channel field-effect transistors, most of them dual-gate MOSFETs for radio-frequency stages. Use the sheet to confirm the pinout of gate 1, gate 2, source and drain, plus ratings and package dimensions, before replacing a suspect device. Small packages often show a marking code rather than the full type, so cross-check it with the document.
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.