Named only 2sd1897, this 35.6 KB PDF is listed as a schematic, yet the name is a JIS transistor number, so it is very likely a compact datasheet. Parts with the 2SD prefix are NPN bipolar transistors designed for low-frequency work. Any PDF reader will open it. Technicians rely on such sheets when a transistor tests shorted, to confirm pinout and maximum ratings and to vet a replacement. Before ordering, check the full marking on the failed device, as package and gain-rank variants exist.
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.