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