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