Documentation for the 2SD1802 in a 150 KB PDF, filed as a schematic though the name suggests a transistor datasheet. Japanese JIS numbering assigns 2SD to NPN bipolar transistors for low-frequency use. Such a sheet gives the pinout, electrical characteristics, maximum ratings and package dimensions needed for diode-mode testing and for choosing a safe substitute with sufficient voltage and current headroom. It opens in any PDF reader. Check the marking on the original part against the sheet before fitting a replacement.
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.