PDF sheet for the 2SK1381 transistor, an N-channel FET in the Japanese 2SK series, about 443 KB in size, which suggests full characteristic graphs and mechanical data. No package or manufacturer is named in the file title, so match the printed marking on the part before relying on the figures. Repair technicians use such documents to look up maximum drain voltage, on-resistance and pin assignment, and to cross-reference a modern replacement when the original is no longer stocked.
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.