{TAIL ~ a plurality} of spaced spherical interrupter elements extending along the said core element, {HEAD ~ the core element} being free of interrupter elements at its ends 
{ TAIL ~ a plurality } of spaced spherical interrupter elements extending along the said core element , { HEAD ~ the core element } being free of interrupter elements at its ends
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH