The 2SD863 transistor datasheet, a 96 KB PDF with no maker named in the file title. JIS numbering identifies 2SD devices as NPN transistors aimed at low-frequency circuits such as audio output, switching and power regulation. Repair work typically calls for the pin diagram, voltage and current limits, power dissipation and gain data found in such a sheet, both to judge whether a part has failed and to select a suitable replacement. Compare the package outline with the board before ordering parts.
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.