From an apparatus standpoint, the invention comprises a sensor assembly carried by {HEAD ~ an upstanding wall member} having {TAIL ~ an elongated opening} 
having
From an apparatus standpoint , the invention comprises a sensor assembly carried by { HEAD ~ an upstanding wall member } having { TAIL ~ an elongated opening }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL