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