A 100 KB PDF whose name is simply the part number 2SC4171; despite the schematic label it is best treated as a transistor datasheet. The 2SC prefix in the JIS system identifies an NPN bipolar transistor, normally marked C4171 on the component itself. Technicians open it in any PDF viewer to look up the pinout, case style and electrical limits when testing a suspect device with a meter or selecting a cross-reference part. The name says nothing about manufacturer or gain class, so verify the suffix letter printed on the original.
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.