The first sub path extracts the second order intermodulation component from {HEAD ~ the path} tuning {TAIL ~ signal} of the main path 
tuning
The first sub path extracts the second order intermodulation component from { HEAD ~ the path } tuning { TAIL ~ signal } of the main path
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH