Reference PDF for the HM9102D, catalogued as a schematic and sized at 467 KB; the name carries only the part number with no device, board or revision information. HM9102D is commonly known as a telephone dialer IC, so the file likely shows pin assignments and an example circuit. A technician can use it to trace keypad and tone or pulse output lines, check supply pins and compare a faulty circuit with the reference design. Open it in any PDF viewer and verify the chip marking and package against the board first.
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.