PDF datasheet entry for the 2SK2986, 433 KB. Only the part number appears in the name; the 2SK prefix tells a technician it is a JIS-registered N-channel FET. Such documents list absolute maximum ratings, electrical characteristics and mechanical dimensions. They help when tracing a fault in a power stage, confirming which leg is gate, drain or source, and deciding whether a modern equivalent can replace an obsolete transistor without exceeding voltage or heat limits.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.