On Wed, Oct 27, 2010 at 1:56 AM, Mark Rages <markrages@gmail.com> wrote:

> An inductive proximity sensor can probably sense the presence of a
> subway train.
>
> Two sensors placed a known distance apart, and measured with accurate
> timer, will give the average speed between them.
>

Or maybe one coil if we know the entire length of the train? So we measure
the drop in and out...

Tamas



>
> Regards,
> Mark
> markrages@gmail
> --
> Mark Rages, Engineer
> Midwest Telecine LLC
> markrages@midwesttelecine.com
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