Category: <b>serial I/O</b>
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<pre><b>INT 6B - NPC NCSI EXTENDED SERIAL I/O - DISCONNECT A VIRTUAL CIRCUIT</b>

	AH = 17h
	AL = virtual circuit number
Return: CF clear if successful
	CF set on error
	???
Note:	this function is also supported by TelAPI, which always returns CF
	  clear and AL=00h
SeeAlso: AH=11h,AH=16h
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