PDF of 31.1 KB on the 2SC5791, an NPN bipolar transistor according to its Japanese 2SC prefix. Although indexed as a schematic, the brief file most likely contains the part datasheet; the name mentions no producer or package. Technicians open it to verify pin assignment, absolute maximum ratings and gain figures while repairing a circuit or seeking an equivalent. Confirm the marking code and package on the PCB agree with the document, because neighbouring part numbers can differ considerably in ratings.
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.