{HEAD ~ The forcer} is {TAIL ~ a periodic device} for incrementally moving in a normally open loop configuration over a toothed base element or platen, and can be a linear or other stepper motor system 
is
{ HEAD ~ The forcer } is { TAIL ~ a periodic device } for incrementally moving in a normally open loop configuration over a toothed base element or platen , and can be a linear or other stepper motor system
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH