each of {HEAD ~ two diametrically opposite sections} of {TAIL ~ the sleeve} has a recess opening to the sleeve inside surface or is radiation permeable to receive and hold the transmitter or the receiver 
of
each of { HEAD ~ two diametrically opposite sections } of { TAIL ~ the sleeve } has a recess opening to the sleeve inside surface or is radiation permeable to receive and hold the transmitter or the receiver
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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