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<p>it is relatively simple to prevent conflicting tokens being handed out.</p>

<p><big> Block signalling </big></p>
<p>Trains cannot collide with each other if they are not permitted to occupy the same section of track at the same time, so railway lines are divided into sections known as blocks. In normal circumstances, only one train is permitted in each block at a time. This principle forms the basis of most railway safety systems. Blocks can either be fixed (block limits are fixed along the line) or moving blocks (ends of blocks defined relative to moving</p><p>
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