----- Original Message ----- 
From: "Alan B. Pearce" <A.B.Pearce@rl.ac.uk>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, February 15, 2006 12:03 PM
Subject: Re: [EE] Speedometer for the model railroad - RF or IR?


> >>  Why don't you build a small transmitter operating
> >>  at say 200Khz or so and capacitively couple the
> >>  modulated signal to the rails
> >
> >That thought occured to me initially but I wondered
> >about the amount of electrical noise from the motor(s)
> >going back on to the track
>
> That is essentially how Marklin do their new mfx loco decoders. In their
> case they use a Radio Data System chip at the controller end as the
> receiver. AFAIK there are patents involved in this, so I suggest you don't
> try and make it commercially ;)

I would suppose that this is not exactly how mfx works :-) mfx is more or
less a further development of DCC done by the german company Doehler & Haas,
the developers of the model railroad controlling system SX. They added 2way
communication to the controlling system and direct decodeable addresses
(which allows a user to know that he controls the locomotive E103 and not an
address 95). All control is done via the rails - so a simple transmitting
system for pulses is state of the art (or behind :-) ).

regards

Enrico



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