{HEAD ~ each} of 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 
{ HEAD ~ each } of 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
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH 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