{HEAD ~ An activation button} exposed through {TAIL ~ the top} of the assembly is depressed to actuate a switch assembly which, in turn, actuates a drive mechanism 
exposed through
{ HEAD ~ An activation button } exposed through { TAIL ~ the top } of the assembly is depressed to actuate a switch assembly which , in turn , actuates a drive mechanism
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH