beginning a control cycle when {TAIL ~ Ri} is between Ro+r and {HEAD ~ Ro} r 
beginning a control cycle when { TAIL ~ Ri } is between Ro+r and { HEAD ~ Ro } r
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH