A 128 KB PDF identified solely by the transistor number 2SC4218. JEITA naming assigns 2SC to NPN bipolar transistors, so despite the schematic label this is most plausibly the component's datasheet. The name says nothing about the maker, package or intended equipment. A technician would open it in any PDF reader to look up pin order, maximum voltage and current, and gain range, then use those figures to diagnose a shorted or open junction or to confirm that a replacement part is equivalent.
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.