Int 2F Fn 3900  - Kingswood Tsr Interface - Compatibility Mode             [t]

   AX = 3900h

Return: AL = status
       00h not installed
       FFh one or more TSRs using this interface is installed
       DX may be destroyed

Note:  this function is provided to that the multiplex number will appear used
     to other programs

See Also: AH=39h/BL=00h