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