# Turnouts and reverse polarity



## rva1945 (Feb 11, 2016)

Hi:

As far as I know (newcomer) the polarity can be reversed when switching a turnout, what happens in DCC?

Thanks


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## CTValleyRR (Jul 26, 2014)

In DC, polarity is used to control the direction of the loco. Some turnouts are power-routing, but they don't reverse the polarity (that comes from creating track that loops back on itself).

In DCC track power is essentially constant. A decoder inside the locomotive takes commands from a command station and decides how much current and what polarity to send to the motor to carry out those commands (speed / direction). You still need to be careful to maintain constant polarity on your rails, though, and any reversing loops must still be isolated and wired through a control unit.


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## gunrunnerjohn (Nov 10, 2010)

I actually hated to do it, but I've removed most of the "discussion" as it was not really addressing the topic.

*rva1945*, I'm sorry this got dumped all over your thread, I can assure you that I'm going to take a more active hand in curbing these side trips from now on.


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## gunrunnerjohn (Nov 10, 2010)

Guys, let's forget about the past and deal with the topic of the thread. 

Thanks.


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## mesenteria (Oct 29, 2015)

rva1945 said:


> Hi:
> 
> As far as I know (newcomer) the polarity can be reversed when switching a turnout, what happens in DCC?
> 
> Thanks


Not really. When you throw the points on a switch/turnout, the polarity of the unused rails adjacent to the point can, in some instances, take the same polarity as the point and stock rail that the owner intends to use with the train. So, yes, they do switch, but the polarity applied to the fed rails is not reversed. That would only be accomplished via a toggle such as a DPDT or by swapping the feeder wires. In DC, that would have the effect of making the locomotive reverse its direction, probably something you had not wanted it to do. Presumably you had wanted it to enter the turnout...?

The same happens in DCC. DCC voltage is actually AC current. It's just that it has an imposed digital signal in the voltage, and the decoders interpret the signal that is really one of your commands to it. When the decoder understands that your signal is for it to make the engine move in reverse, it is receiving a voltage with different information.


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## Overkast (Jan 16, 2015)

rva1945, beleow is one of my posts from another thread that shows an illustration about a reverse polarity situation and explains it:



Overkast said:


> WIrailfan, since you are still a bit unclear on what a reverse loop is, I drew up a diagram that hopefully explains the scenario better:
> 
> 
> 
> ...


Does that help at all?


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## ED-RRR (Jun 4, 2015)

*Directly to [rva1945]..*

*[rva1945]:* Hi

RE: Turnouts and reverse polarity.. This "Thread"..
Please clarify your question..

*Question:*
Are you "Only" talking about "Switch Tracks" ??
- OR -
Are you "Only" talking about "Reverse Loops" ??
......


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