Int 2F Fn 1505  - Cd-rom - Read Vtoc                                       [d]

   AX = 1505h
   ES:BX -> 2048-byte buffer
   CX = drive number (0=A:)
   DX = sector index (0=first volume descriptor,1=second,...)

Return: CF set on error
       AX = error code (15=invalid drive,21=not ready)
   CF clear if successful
       AX = volume descriptor type (1=standard,FFh=terminator,0=other)

Note:  This function was not supported by Novell DOS 7 NWCDEX prior to the
     08/16/94 update