A first stage of {HEAD ~ the interpolation circuit} calculates a one half amplitude value; a second stage calculates {TAIL ~ one fourth and three fourths amplitude values}, and a third stage calculates one eighth, three eighths, five eighths, and seven eighths amplitude values 
A first stage of { HEAD ~ the interpolation circuit } calculates a one half amplitude value ; a second stage calculates { TAIL ~ one fourth and three fourths amplitude values } , and a third stage calculates one eighth , three eighths , five eighths , and seven eighths amplitude values
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH