I was involved with a model railroading club several years ago, and we
used a product called On Track to control all of our trains.  Basically,
it was a tiny microprocessor that recevied a modulated signal from the
rails and controlled speed and direction of the electric motor.  It even
had a tiny speaker to make realistic air-horn noises.  Maybe someone out
there knows how they work...

-JC

John Mullan wrote:

> Is there some simple circuit for using the 2 rails of the model
> railroad as the network connection (ie: PICs on the engine receiving
> commands via the rails)?
>
> Is there a simple but cheap alternative to this method?
>
> RF seems like extra work, circuitry and expense.
>
> John Mullan