Int 14 Fn 2C  - Hunter 16 - Set Dtr                                        [S]

   AH = 2Ch
   AL nonzero
   BL = new state
       00h  normal operation
       else force DTR high

Return: AH = 00h
Desc:  determine whether the DTR signal on COM1 should be forced high

See Also: AX=2C00h