{HEAD ~ The shuttle element} may serve as {TAIL ~ an indicator} or signaling element, either alone or together with the above described functions, so as to signal to a sensor that the transition or boundary between the paint and the auxiliary medium has reached a certain sensing location 
{ HEAD ~ The shuttle element } may serve as { TAIL ~ an indicator } or signaling element , either alone or together with the above described functions , so as to signal to a sensor that the transition or boundary between the paint and the auxiliary medium has reached a certain sensing location
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH