With this variant, the input signal {HEAD ~ S1} is fed directly to {TAIL ~ the non linear network} in front of the amplifier 4 
With this variant , the input signal { HEAD ~ S1 } is fed directly to { TAIL ~ the non linear network } in front of the amplifier 4
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH