The four bar linkage is a parallelogram type linkage which enables {HEAD ~ the jogger plate} to maintain {TAIL ~ its orientation} in space regardless of any swinging movement experienced by the parallelogram linkage 
The four bar linkage is a parallelogram type linkage which enables { HEAD ~ the jogger plate } to maintain { TAIL ~ its orientation } in space regardless of any swinging movement experienced by the parallelogram linkage
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH