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