# Two way DCC?



## traction fan (Oct 5, 2014)

Has anyone heard about DCC standards changing to include two way data communication between DCC throttles and loco decoders? This was briefly mentioned in some of Kalmbach's
DCC "how to" books as something "just around the corner". I think a form of it is used with the expensive new "Surround Sound" system. The basic concept is that feedback data packets from the decoder to the command station, help locate the locomotive's position, on the layout, and the sound is channeled to the external speaker nearest the train. So far this locating feature only works with DigiTrax systems. I use NCE, but the surround sound system is so expensive that I can't afford it anyway! I'm just curious to find out if the NMRA or the manufacturers have come up with anything new on this.

Traction Fan :dunno:


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## mopac (Feb 24, 2011)

Reading CVs would be 2-way communication. They have that now.
It would be cool with a lot more info being sent to throttle. I haven't
heard of anything new. I guess the new paragon3 bli locos send
some signals but I am guessing that is just for sound.


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## Cycleops (Dec 6, 2014)

I think something like surround sound will have you reaching for the ear plugs!


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## irishthump (Jul 1, 2013)

mopac said:


> Reading CVs would be 2-way communication. They have that now.
> It would be cool with a lot more info being sent to throttle. I haven't
> heard of anything new. I guess the new paragon3 bli locos send
> some signals but I am guessing that is just for sound.


Reading CV's is not 2-way communication as such since you have to place a loco on a seperate programming track to read a CV. There is no 2-way communication on a standard DCC layout, the command station constantly communicates with the decoder but the decoder never answers back!

Railcom is a 2 way system from Lenz but it has only been adopted by a handful of European manufacturers.


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## fcwilt (Sep 27, 2013)

This is likely what you are thinking of and it's Railcom roots was mentioned by another poster.

http://www.mrsonline.net/html/railcom.html


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## higgsbosonman (Nov 17, 2014)

this is already possible, it's just absurdly expensive. I know that JMRI will locate the engines on the layout based on which block or subblock is drawing power, and it simply tracks the engine as it goes from one block to another. It always keeps at least one block of seperation between the locomotives, so it can't mix them up. I believe this is the Digitrax system you mentioned, and I know JMRI supports NCE, but you still need dozens of electrical blocks. 

This still isn't quite decoder-to magic box communication, but honestly, what could the decoder say? they don't know where they are on the layout; they only know their throttle setting, and if their headlights and stuff are on. They don't even know if they are moving, because no engines are equipped with feedback sensors to their wheels, except sound equipped engines with the chuff sync, but that only tells it if the wheels are moving, not if the wheels are slipping. Block detection (like what real railroads use) is the only viable option. Maybe in the future, we'll have accelerometer equipped engines, but inertial guidance would only help with tractive effort and smoother momentum control.

We're also dealing with standards that are kind of ancient. the current DCC systems are 15 years old or older. They work, but we have new technology that can't easily be implemented into them without people buying new systems, and the features would still be kind of meh.


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## fcwilt (Sep 27, 2013)

The decoder could report it's current status (functions, speed step) and perhaps most importantly it's address.

So a system like JMRI (or other automation software) could determine what engine is in what block, assuming your layout is blocked for this purpose.

The Digitrax system that can perform this requires a good deal of addition wiring and can be hard to get working.

A Railcom like system would require no special wiring other then a compliant command station and decoders.


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