Covering the 2SD2645, this 29.3 KB PDF sits in the schematic index although the name suggests a component datasheet. The 2SD prefix follows the JIS standard for NPN low-frequency transistors. Expect pin configuration, absolute maximum ratings, electrical characteristics and package dimensions, which are the details needed when testing a suspected shorted junction or sourcing a replacement. Any PDF viewer displays it. Make sure the physical part marking corresponds to this number, as similar type numbers can have quite different ratings.
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.