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