first summing amplifier means for generating {HEAD ~ a left right summing output signal} which is {TAIL ~ a function} of the sum of said left and right output pulses 
is
first summing amplifier means for generating { HEAD ~ a left right summing output signal } which is { TAIL ~ a function } of the sum of said left and right output pulses
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH