Reference sheet for the 3SK143, delivered as a 35.1 KB PDF and indexed under schematics. Beyond the part number the name says nothing. The JIS code 3SK designates a four-terminal N-channel FET, typically a dual-gate MOSFET used in VHF and UHF front ends. Technicians consult such a sheet for the lead arrangement, which is easy to get wrong on tiny packages, and for drain voltage, gain and noise figures when hunting for an equivalent in a radio or TV tuner repair.
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.