second summing amplifier means for generating an up down summing {HEAD ~ output signal} which is {TAIL ~ a function} of the sum of said up and down output pulses 
is
second summing amplifier means for generating an up down summing { HEAD ~ output signal } which is { TAIL ~ a function } of the sum of said up and down output pulses
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH