PDF document whose Persian title translates as datasheets of amplifier ICs, filed here as a schematic but in practice a reference collection for audio amplifier chips. At 132 KB it is a short file, likely holding pinouts, typical application circuits or a summary table rather than full manufacturer datasheets. Technicians use such material to identify supply pins, outputs and mute or standby inputs when testing an amplifier stage. Any PDF reader opens it, and pin numbers should be checked against the marking on the actual chip package.
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 @datasheets1. 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.