An external backing material matched to the acoustic impedance of the CdS crystal is attached to {TAIL ~ the electrode} connected to {HEAD ~ the signal processing system} 
An external backing material matched to the acoustic impedance of the CdS crystal is attached to { TAIL ~ the electrode } connected to { HEAD ~ the signal processing system }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD