The platform alternatingly moves in either one of a direction substantially similar to the direction of motion of the conveyor, and a direction substantially opposite to the direction of {HEAD ~ motion} of {TAIL ~ the conveyor} 
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The platform alternatingly moves in either one of a direction substantially similar to the direction of motion of the conveyor , and a direction substantially opposite to the direction of { HEAD ~ motion } of { TAIL ~ the conveyor }
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 OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL