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