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