Tom Anderson wrote:
snip
Using the running rails as a voltage reference would be the obvious
way to do it. AIUI, there is a voltage across them from track
circuits, but it's small enough that it shouldn't matter.


When the train is there the running rails are at the same potential, the
train axles providing the short circuit between them.


--
Cheers for now,

John from Harrow, Middx

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