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