A production line has {HEAD ~ a plurality} of {TAIL ~ working groups} in which work operations are controlled by a sequential controller 
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A production line has { HEAD ~ a plurality } of { TAIL ~ working groups } in which work operations are controlled by a sequential controller
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