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