Document 1, wherein {TAIL ~ said regions} made of magnetic material are spaced by {HEAD ~ magnetically blank portions} 
Document 1 , wherein { TAIL ~ said regions } made of magnetic material are spaced by { HEAD ~ magnetically blank portions }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD