The belts are twisted 180 degrees between the entrance and exit pulleys with each having {HEAD ~ at least one span} contiguous to {TAIL ~ a corresponding span} of the other 
contiguous to
The belts are twisted 180 degrees between the entrance and exit pulleys with each having { HEAD ~ at least one span } contiguous to { TAIL ~ a corresponding span } of the other
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH