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