At {TAIL ~ other angles}, {HEAD ~ the belt} is prevented from jumping out of the pulley 
At
At { TAIL ~ other angles } , { HEAD ~ the belt } is prevented from jumping out of the pulley
REL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH