This 246 KB PDF bears only the part number 2SC5110 and, despite its schematic label, should contain the datasheet for that device. A JIS name starting with 2SC indicates an NPN bipolar transistor, usually marked C5110 on the body. Technicians turn to such a document to locate base, collector and emitter pins, confirm the package type, and read collector-emitter breakdown voltage, current limits and gain, all of which matter when diagnosing a dead stage or picking a cross-reference.
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.