INT 2F - FaxBIOS interface - INSTALLATION CHECK
        AX = 8000h
        DX = 0000h
        DI = 0000h
Return: AL = FFh if installed
        DX:DI -> signature "FaxBiosjpc"
Note:   FaxBIOS may use any multiplex number from 80h through FFh; to determine
          whether it is installed, it is necessary to poll all multiplex
          numbers for one which returns the above signature
SeeAlso: AH=2Ah,AX=80FBh

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