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