{HEAD ~ The second sensor} 20 is referred to as {TAIL ~ the nearly collocated sensor}, and is installed near the actuator 14 but outside its realm of direct influence 
{ HEAD ~ The second sensor } 20 is referred to as { TAIL ~ the nearly collocated sensor } , and is installed near the actuator 14 but outside its realm of direct influence
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH