Named only 2SC4161, this 98.6 KB PDF is categorised as a schematic yet, judging by the part number, documents an NPN bipolar transistor under the JIS designation scheme. On circuit boards such parts usually carry the marking C4161. Open it in a PDF reader to find pin order, package dimensions, maximum collector voltage and current, and gain figures before testing or replacing the device. The name does not reveal manufacturer or revision, so confirm the original part's marking and footprint to avoid fitting a mismatched substitute.
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.