Thus, {HEAD ~ a touch point C} in {TAIL ~ the detecting area} 219 can generate a mirror point C1 
in
Thus , { HEAD ~ a touch point C } in { TAIL ~ the detecting area } 219 can generate a mirror point C1
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH