The drive mechanism may also include either a set of timing gears or {TAIL ~ a spring coupling} to achieve {HEAD ~ the desired intermittent rotation} 
The drive mechanism may also include either a set of timing gears or { TAIL ~ a spring coupling } to achieve { HEAD ~ the desired intermittent rotation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD