Small 41.6 KB PDF dedicated to the 2SC3704, classified here as a schematic yet in practice a component reference. The E suffix in the name is unexplained and likely just marks the document edition. JIS part numbers starting with 2SC refer to NPN transistors. The sheet is useful for confirming which pin is which on the package, reading the collector-emitter breakdown voltage and maximum current, and comparing those with a proposed equivalent before soldering it into a repaired circuit.
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.