Compact 38 KB PDF datasheet for the 2SD2142K, an NPN transistor named in the Japanese JIS scheme, where the trailing letter marks a specific package or variant. Technicians rely on such documents to read the marking code, lead order and electrical limits of small transistors that are hard to identify on a crowded board. It also helps when searching for a substitute with matching gain and voltage rating. Check that the suffix of the part fitted matches, since lettered variants can differ in package.
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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