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Trainee pensioner
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I don't want to repeat what others have said, but sometimes, the same information given in a different way can help. So I hope this helps!
When you create a reverse loop you effectively connect the "positive" and "negative" (or left and right) rails together, forming a short circuit. To prevent the short circuit occurring, insulating fishplates are fitted at both ends of the reverse loop (creating an isolated section) and the output of the reverse loop module (RLM) is connected to the isolated section. The input of the RLM is connected to the main track circuit bus or controller output.

The RLM will supply the power to the isolated section and when the loco enters the section it will set the polarity of the rails in the isolated section correctly to match the polarity of the input track so that no short circuit occurs.

When the loco leaves the isolated section at the other end of the loop, it will re-set the polarity to match that of the exit track

The isolated section should be longer than the longest train if metal wheels are fitted because they will cause a temporary short circuit as they pass over the track joints, even with insulated fishplates. Plastic wheels on the coaches/wagons won't cause this problem, so in this case the isolated section can be as short as the longest loco. (but plastic wheels are best avoided)
 
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