A schematic diagram. Shared as “TDA 7294 PLUS PSU (SFILE.MOBI).pdf” — a .pdf file, 809 KB.
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 @pdf_servicemanual. 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.