Covering the 2SC5198, this 171 KB PDF sits in the schematic category but carries only a transistor part number, so treat it as a datasheet. The 2SC prefix follows the Japanese JIS scheme for NPN high-frequency transistors. Typical sections give lead assignment, absolute maximum ratings, electrical characteristics and dimensions. Identical file sizes to adjacent 2SC519x files suggest a common document, so check that the parameters listed actually refer to the 2SC5198 before using them.
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.