an analog to digital converter that converts {HEAD ~ an analog acoustic input signal} into {TAIL ~ a digital input signal} 
an analog to digital converter that converts { HEAD ~ an analog acoustic input signal } into { TAIL ~ a digital input signal }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL