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> Something like this (Attachment)?

More like this. I have similar switches, not 30m wires though,
running past petrol motors and RT radios with no problems.
Plenty of noise around too

> Is this a better solution than optoisolator?

Hard to say. The input to the opto could also be noisy. It's
something you'd have to sort out on site with a scope to be
absolutely sure


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