The 2SC3099 is the only detail this 318 KB PDF name gives, and the file is indexed as a schematic, although it is probably a datasheet. The 2SC prefix in the JIS scheme denotes an NPN bipolar transistor for high-frequency service. Before replacing the part, a repair tech can use the document to verify the package pinout, voltage and dissipation limits and gain grade. The file does not name a manufacturer, so match the printed marking and the circuit position before choosing an 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.