# BXP88 vs BDL168 rail A/B confusion



## KeithStansbury (Oct 23, 2019)

Before I install a new (first) BXP88...

I noticed in the BXP88 doc (pic pg 7) it shows rail A as common. I read in the doc (note after 5.0.6 pg 6) that rails A and B must be consistent.

Having struggled with Digitrax documentation in the past, I checked the BDL168 doc to confirm this "consistency". Curiously, I find the direct home wiring pic (pg 6) shows rail B as common.

So - if I follow the digitrax installation pictures from their docs, will I have the polarity problem they warn about? I'm already running with a BDL168 wired as shown in its respective doc.

Thanks
Keith


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## D&J Railroad (Oct 4, 2013)

I think the objective is to establish a common rail (period). Call it rail A, Rail B, rail 1, rail 2 or whatever as long as it is separate from the other rail over the entire layout.


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## Lemonhawk (Sep 24, 2013)

You might need to be consistent over the whole layout with what is the common rail and a BXPA1 on the reverse loops. I'm thinking that you would run into problems crossing from an area controlled by 1 BXP88 to another BXP88. Be nice to know all this for sure before I install my BXP88's also Kieth!


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