Documentation for the 2SC4781 in a 120 KB PDF, indexed as a schematic though the name matches a discrete semiconductor part. In the JIS designation system, 2SC identifies an NPN bipolar transistor. No package, maker or revision information appears in the name. On the repair bench it is used to look up the pin arrangement, absolute maximum ratings and characteristic data. That helps when a suspected transistor has to be tested, replaced or matched with an equivalent, so verify the marking first.
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.