Part number 2SC4157 is the only clue in the name of this 125 KB PDF, which sits under schematics but is effectively a transistor datasheet. Japanese JIS designations reserve 2SC for NPN bipolar transistors, usually marked C4157 on the device. The sheet helps confirm pin assignment, case outline and rated limits when checking for a shorted junction or choosing a substitute in an amplifier or switching stage. No manufacturer, revision or grade appears in the name, so match the original component's marking 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.