In addition, {HEAD ~ each drive roller} has its own drive motor so it can be driven independently in {TAIL ~ either direction} about the common axis 
In addition , { HEAD ~ each drive roller } has its own drive motor so it can be driven independently in { TAIL ~ either direction } about the common axis
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH