Document for the 3DD304X, stored as a 489 KB PDF and catalogued under schematics, though the name suggests a component datasheet. The name carries no further details such as ratings or package, so the contents should be checked on opening. Devices with a 3DD prefix follow Chinese transistor numbering commonly used for power transistors in power supplies and lighting ballasts. A technician would use the sheet to confirm pinout and limits before replacement, and should compare any substitute carefully against the voltage and current figures given.
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.