Int 14 Fn 87  - Comm-drv V14.0 - Turn On Dtr                               [S]

   AH = 87h
   DX = port number

Return: AH bit 7 set on error
   AH bit 7 clear if successful

See Also: AX=8000h"COMM-DRV",AH=88h"COMM-DRV",AH=89h"COMM-DRV"