{HEAD ~ A platform} is positioned above {TAIL ~ the conveyor} and is capable of alternatingly moving in either one of a first direction, substantially similar to the direction of motion of the conveyor, and a second direction, substantially opposite to the direction of motion of the conveyor 
{ HEAD ~ A platform } is positioned above { TAIL ~ the conveyor } and is capable of alternatingly moving in either one of a first direction , substantially similar to the direction of motion of the conveyor , and a second direction , substantially opposite to the direction of motion of the conveyor
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH