{HEAD ~ A tensioning drive} is provided at one end of {TAIL ~ a section} of the predetermined course 
{ HEAD ~ A tensioning drive } is provided at one end of { TAIL ~ a section } of the predetermined course
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH