The drivers are driven such that they carry out {HEAD ~ a conveying displacement} in {TAIL ~ the conveying direction} and a return displacement in the opposite direction 
in
The drivers are driven such that they carry out { HEAD ~ a conveying displacement } in { TAIL ~ the conveying direction } and a return displacement in the opposite direction
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH