The control center knows at {TAIL ~ any time} by {HEAD ~ radio contact} where the train is traveling 
The control center knows at { TAIL ~ any time } by { HEAD ~ radio contact } where the train is traveling
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH