The two sets of two coils are positioned on {HEAD ~ two different sides} of {TAIL ~ the array} 
of
The two sets of two coils are positioned on { HEAD ~ two different sides } of { TAIL ~ the array }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL