{TAIL ~ The optical touch device} can avoid {HEAD ~ a blind zone} and can be used as a dual touch device or a multi touch device 
{ TAIL ~ The optical touch device } can avoid { HEAD ~ a blind zone } and can be used as a dual touch device or a multi touch device
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH