INT 6B - Novell NASI/NACS, Ungermann-Bass Net One SERIAL I/O - CONTROL          
	AX = 0600h
	CX = command
	    02h send break
	    04h disconnect
	    06h hold
Return: CF clear if successful
	    AL = 00h
	CF set on error
	    AX < 0
Note:	this function is also supported by TelAPI and NPC NCSI