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  1. #1
    Unknown Device wratterus's Avatar
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    Default Does phone line polarity affect DSL performance

    I've not been able to find a solid answer to the above question. I suppose I could test it for myself by reversing the cable pair and checking line stats, but does anyone know for sure?
    Last edited by wratterus; 31-05-2016 at 05:54 PM.
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  2. #2
    In a 1920s time warp Terry Porritt's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    I'd have thought no, but Silicon Chip magazine had a polarity checker, and suggested incorrect polarity could cause slow ADSL with some modems.
    http://archive.siliconchip.com.au/cm...5/article.html

  3. #3
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    Default Re: Does phone line polarity affect DSL performance

    In the thousands of dsl lines I've worked on I have never known it to make a difference.Doesn't make a difference to the phone so shouldn't make a difference to the dsl

  4. #4
    Smiling Down On Youse SurferJoe46's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    Wouldn't the phone company detect the reversed polarity - if it was true - and send an agent out to correct it with or without your calling to bring it to their attention?

    You've only got one twisted copper pair - right - in Upsidedown land?

    That's why you put as Low-Pass (I think, or maybe a High-Pass) filter on the phones - right?


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  5. #5
    amateur expert dugimodo's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    Not as a rule. Once upon a time some phones or phone systems particularly older pabxes were polarity concious and had problems like one ring only if reversed. It does cause issues for phones sometimes if the polarity changes between jackpoints and you have multiple phones connected. You really should have the wiring straight within the house at least.The ADSL signal is a balanced signal and filtered off and it's an AC signal so it doesn't really have a polarity so in theory it really should make no difference at all. In practice though weird stuff can happen that doesn't make sense so sometimes it's worth trying the stuff the really shouldn't matter

    Also the cable pair to your house can pass through several points where it can be reversed and installers while usually consistant in their wiring practices pay no particular attention to polarity at any of them so it could switch back and forth multiple times between the cabinet/exchange and your house. At the end of the day if you ignore the colour there's not really a difference between one wire and the other.

    Short version:- No
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  6. #6
    Unknown Device wratterus's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    Thanks guys.
    Microsoft: "You've got questions. We've got dancing paperclips."

  7. #7
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    Default Re: Does phone line polarity affect DSL performance

    Quote Originally Posted by SurferJoe46 View Post
    You've only got one twisted copper pair - right - in Upsidedown land?
    Yes but do ours twist the same direction as yours ??

  8. #8
    Smiling Down On Youse SurferJoe46's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    They twist in the same direction, but somehow the US twists are much tighter.


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  9. #9
    amateur expert dugimodo's Avatar
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    Default Re: Does phone line polarity affect DSL performance

    We're just more relaxed is all. Maybe because the internet flows downhill to get here. Plus our wires are metric which clearly works better in the digital age, no Jamming of square pulses into round AWG gauges going on here, so we don't need to wind them up so tightly to compensate.
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