More precisely, the comparator 92 compares the density represented by each dot signal, with {HEAD ~ the reference density} represented by {TAIL ~ the reference data} 
More precisely , the comparator 92 compares the density represented by each dot signal , with { HEAD ~ the reference density } represented by { TAIL ~ the reference data }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL