At the check nodes, each check node determines the modulo 2 sum of the incoming bits in {HEAD ~ a similar fashion} shown in {TAIL ~ the sign component} of FIG 17 and checks if the sum is zero or not 
At the check nodes , each check node determines the modulo 2 sum of the incoming bits in { HEAD ~ a similar fashion } shown in { TAIL ~ the sign component } of FIG 17 and checks if the sum is zero or not
OTH OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH