Datasheet for the 2SD2650 transistor, a 29.7 KB PDF filed in the schematic category. The file name states the part number and nothing else. The JIS 2SD prefix identifies an NPN bipolar transistor for low-frequency circuits. A technician would open it in any PDF reader to confirm pin assignment, collector-emitter voltage, collector current and dissipation, then use those figures to qualify a substitute and to check that the component on the board was not run beyond its limits.
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.