PDF of 111 KB named for the 2SC2078 transistor, stored in the schematic category of the index. Under JIS conventions the 2SC prefix denotes an NPN bipolar device, making this most likely the manufacturer datasheet. It is useful for confirming emitter, collector and base positions, reviewing maximum ratings and reading frequency or gain characteristics before swapping a part. The file name carries no revision or maker information, so cross-check the physical marking and package on the board with the drawing inside.
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.