Datasheet for the 2SD1815 in PDF format, 154 KB, catalogued as a schematic. Apart from the type number, the name carries no extra details. The JIS scheme classifies 2SD parts as NPN transistors for low-frequency applications. Technicians open this kind of sheet to identify collector, base and emitter, check breakdown voltages and collector current limits, and compare the package drawing with the PCB footprint before fitting a replacement. Any PDF viewer works, and the marking on the original component should be checked first.
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.