Datasheet-style PDF for the 2SK1840, sized 87.3 KB. Part numbers beginning with 2SK are registered under the Japanese JIS scheme for N-channel field-effect transistors. The file name carries no maker, package or revision information. Such sheets are opened in any PDF reader and used to confirm the pin arrangement, the breakdown voltage and the drain current limit. On the bench this helps decide whether the transistor is failed by comparing diode-mode readings across its pins, and which replacement will fit safely.
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.