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A train crosses the road and passes beyond the crossing island circuit. ("Island" is the section of track over the road and a short distance beyond on each side of the road.) If the train stops before leaving the trailing crossing circuit, and backs, the (o)T(o) will not operate until the wheels shunt the island. Correct?
I think it depends on the type of hardware that controls the signal. There are newer signal controls which use computers to determine speed and direction of travel. These would be able to detect the train stoping and then backing up. I used to switch the POTB in Tillamook and the 3rd St. signal was this way. If the signal has older equipment, i.e. relays, it will probably operate in the manner of you question.
A relay 3 DC track circuit will not see the train reverse if it never gets off the 3rd track circuit since a stick relay is stuck. Some crossings now have timers that when the time expires the stick is released.
A newish crossing will see the train if it is equipped with a predictor. It can tell if the train is moving closer to the island, or further away.
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