Covers the 2SD1826 in a 152 KB PDF; the index labels it a schematic, but a bare part number like this normally means a component datasheet. Under JIS numbering, 2SD marks NPN bipolar transistors for low-frequency applications. Use it to identify the pinout and package and to compare maximum ratings against the circuit before swapping parts. Bodies are often marked only D1826, so match that short code carefully against the number.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)