The 2SD1907 is covered by this 165 KB PDF, which is catalogued as a schematic but by name is a component datasheet. The 2SD designation in Japanese JIS numbering covers NPN transistors for low-frequency circuits, and no other details appear in the name. Technicians use such a sheet to locate the base, collector and emitter terminals, read the absolute maximum ratings and confirm that a replacement can handle the same load. Any PDF viewer opens it. Check the case marking, often reduced to D1907, and the package outline 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.