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