An encoder converts {TAIL ~ the digital data} into {HEAD ~ audio tones} that synthesize frequency characteristics of human speech 
An encoder converts { TAIL ~ the digital data } into { HEAD ~ audio tones } that synthesize frequency characteristics of human speech
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH