On {HEAD ~ the outer peripheral surface} of the bobbin main portion is wound with {TAIL ~ a primary windings} 
is wound with
On { HEAD ~ the outer peripheral surface } of the bobbin main portion is wound with { TAIL ~ a primary windings }
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL