Datasheet-style PDF of 118 KB for the 2SD1898, recorded in the index as a schematic but named after a single component. The JIS prefix 2SD indicates an NPN bipolar transistor of the low-frequency category. Bench use is straightforward: look up the pin order for the package, the collector-emitter voltage and collector current limits, and dissipation before choosing an equivalent. Physical parts often carry the number without the 2S prefix, so match the remaining digits and any suffix letter to the document.
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.