Indexed as a schematic, this 199 KB PDF actually carries only the part number 2SC1959, pointing to a single NPN bipolar transistor under the JIS naming scheme. The content is therefore probably its datasheet, covering pin assignment, package, maximum ratings and typical curves. Repair technicians use it to confirm which lead is the collector before probing, to judge whether measured junction readings are plausible and to vet replacement parts. Verify that ratings of any substitute are at least equal to the original.
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.