A PDF of about 318 KB covering part 2SC3098, likely the datasheet for that device even though it is catalogued as a schematic. Japanese JIS designations beginning with 2SC refer to NPN bipolar transistors in the high-frequency category. Typical uses are confirming which lead is collector, emitter or base and checking breakdown voltage and collector current. It also helps when comparing hFE classes against a donor or substitute part. Make sure the body marking really matches before trusting the figures.
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.