{HEAD ~ A platform} is positioned above 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 {TAIL ~ the conveyor} 
{ HEAD ~ A platform } is positioned above 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 { TAIL ~ the conveyor }
HEAD HEAD HEAD HEAD HEAD HEAD 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 OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL