A spring on {HEAD ~ the other end} of the collette presses the collette against {TAIL ~ the shell} to produce wiping contacts at the opening 
A spring on { HEAD ~ the other end } of the collette presses the collette against { TAIL ~ the shell } to produce wiping contacts at the opening
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH