The 2SA1370 is a PNP transistor in the Japanese JIS numbering system, and this 138 KB PDF is named after it alone. That suggests a datasheet rather than a circuit diagram, despite the schematic label. Typical uses during repair include confirming base, collector and emitter pins, reading the collector-emitter voltage limit and the hFE grade, and looking up the complementary NPN type. Body markings usually drop the 2S prefix, so expect to see A1370 on the part itself.
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.