Datasheet in PDF format for the 2SC4161, 130 KB in size. The 2SC prefix in Japanese JIS numbering identifies an NPN bipolar transistor, and the sheet should give voltage and current ratings, dissipation, gain, switching characteristics and the package pinout. Repair work uses it to identify pins, verify a replacement can withstand the same stresses and check whether measured junction behaviour is normal. Open it in any PDF reader, and compare the code printed on the component and its package style with the drawing before ordering parts.
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.