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