Datasheet-style PDF, 469 KB, for the 2SC5091 NPN transistor, listed in the schematic section of the index. Nothing else is given in the name, so manufacturer, package and revision remain unknown. Technicians use such sheets to confirm collector-emitter voltage, collector current, power dissipation, frequency characteristics and the pinout when testing with a multimeter or picking an equivalent. A separate 2SC5091FT variant exists, so verify the exact marking and suffix on the original component before ordering a replacement.
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.