Quote:
Originally Posted by hairyhandedfool
infra red beams to detect trains passing signals but how that could work in real life is anyones guess, badly I suspect.
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The question is how you would be 100% sure that it was a train that was tripping the beams and not a bird, wandering badger or a couple of kids waving branches in front of the detectors.
But it would have to be sensitive enough that every time a real train passed it would trip the beam.