Component documentation for the 2SD1881 transistor, supplied as a 90.6 KB PDF and catalogued as a schematic, though a part number like this normally points to a datasheet. The 2SD prefix in Japanese JIS numbering identifies an NPN low-frequency bipolar device. Technicians use such sheets to read the pin order, package outline, collector-emitter ratings and power dissipation when a failed part must be replaced. On the board the device may simply be stamped D1881, so match the marking carefully.
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.