Jeff Cesnik wrote:

> 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...
>
>
I believe On Track was made by Keller Engineering in Florida. I believe
they used DTMF tones for their control commands (you didn't hear them,
of course). Used a constant DC track voltage with DTMF tones
superimposed on the DC.

Some other command control systems: (or more than you never wanted to
know about ....)

Lionel - 1946 - Variable voltage AC track power (for speed) with single
tone (one or two channel) receivers. A one tube transmitter generated an
unmodulated carrier. Each receiver had an LC resonant circuit that would
activate a relay to control reversing unit, operating car, coupler etc.
Probably the first commercially made command control system.

GE - 1960 - Astrac. Offered (I think 6 channels). Constant voltage AC
track power. Used amplitude modulated carrier for each channel.
Locomotive module could handle 1 amp max. Amplitude was demodulated to
control speed. Years later (mid '70s) a company in Dayton, Ohio called
Alphatronics started making an improved and compatible system with added
channels and higher current loco modules.

Digitrac (later CTC-16) - I can't remember the original creator of
Digitrac. This came out in the early '70s. Used a continuous stream of
16 (8 originally?) bits. Decoder module used a PLL to lock on to the bit
stream. Each bit was a "channel". Control scheme was something like bit
width controlled speed and direction.

Triang Hornby - 1980 - Zero One. First commercial "intelligent" command
control system. Decoder modules used a TI embedded controller. Units
were addressable as devices. I believe that DCC is based on this system.
Anyone know?

Solta - ~1980 - Offered a system which had 4 or 5 or 6 (I forget)
channels which offered the capability of having one train without a
decoder module operate on the same track as ones with modules. The
un-equipped train had variable speed and independent direction. I always
wondered how this system worked. It was very expensive. Seemed to be
most popular with G gage enthusiasts.

I also remember some one in the late '70s selling a loco mounted module
which used R/C servo motors to drive a pot which in turn controlled the
train speed and direction. And Railroad Model Craftsman did and article
about adapting a whole R/C system to a train.

Then there's Lionel's Trainmaster and a system by Marklin which I know
very little about. Anybody have any other systems I've left out?

And the only system which has "won" is DCC, simply because its an
independent standard, which means multiple suppliers and sources for
components. Quite a few DCC decoder modules I've seen in ads use PICs.

-Frank


Frank Richterkessing

FRANK.RICHTERKESSING@APPL.GE.COM