Where the primary core is formed in {HEAD ~ the shape} of {TAIL ~ square ring}, the end faces at both ends of the secondary core are in contact with two sides of the primary core at inner side surfaces thereof facing with each other 
Where the primary core is formed in { HEAD ~ the shape } of { TAIL ~ square ring } , the end faces at both ends of the secondary core are in contact with two sides of the primary core at inner side surfaces thereof facing with each other
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH