Part documentation for the 2SD2579, provided as a PDF of 43.3 KB under the schematic heading. According to the JIS scheme, 2SD denotes an NPN bipolar transistor for low-frequency work, so the file is most likely a datasheet. No manufacturer, package or revision details appear in the name. Use it for pin identification, absolute maximum ratings and gain specifications, and cross-check the marking on the suspect component so that the numbers apply to the device actually fitted.
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.