A subtracting unit subtracts the input signal from {HEAD ~ the first delayed signal} to generate {TAIL ~ a difference signal} 
to generate
A subtracting unit subtracts the input signal from { HEAD ~ the first delayed signal } to generate { TAIL ~ a difference signal }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL