Device 2 or 3, wherein said grid further comprises at least one return connection , linking together two sides of said frame , {HEAD ~ the grid} being made from {TAIL ~ an electric conducting material} 
made from
Device 2 or 3 , wherein said grid further comprises at least one return connection , linking together two sides of said frame , { HEAD ~ the grid } being made from { TAIL ~ an electric conducting material }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL