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I am in Switzerland. Our landline is delivered through an unshielded twisted pair cable.

Are the wires in the pair swappable ? Or does it have a polarity ? The lines is supposed to provide ADSL without POTS. POTS is now deprecated here and the service is no longer available at the telephone socket directly.

Blup1980
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  • Why don't you just try it and see. In my experience POTS / ADSL doesn't care about polarity at all. So yes, you can swap the wires. – Bimpelrekkie Apr 05 '19 at 12:58
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    @Bimpelrekkie. Well, I could try. But I prefer trying after confirmation that it won't damage anything... – Blup1980 Apr 05 '19 at 13:33
  • Some old POTS phones do not work with ring and tip swapped. Sound is OK, but the keypad does not work. – stark Apr 05 '19 at 13:39
  • Proper confirmation can only be given by the telecom / ADSL provider and/or the manufacturer of your ADSL modem. You will never receive this confirmation as they usually don't know how to handle technical questions like this. I can only share my insights. In my opinion nothing can be damaged as POTS / PSTN works with AC voltages up to 80V so all devices connected to it (inclusing ADSL modems) must be able to handle that. I have worked with extending telephone lines many times and never cared about polarity and never damaged anything. You could also ask an ADSL technician if you find one. – Bimpelrekkie Apr 05 '19 at 13:39
  • FYI: I don't know how it is in Switzerland, but phone company techs where I live say, "dry pair," when they talk about a local loop that is paid for by a subscriber, but which does not provide POTS. I used to have ADSL on a dry pair at my house at a time when all my neighbors had ADSL + POTS; and when I had questions about my service, the phrase, "dry pair," worked like magic to dispel confusion. – Solomon Slow Apr 05 '19 at 14:52
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    In most POTS/ADSL installations, the DC bias is swapped at the exchange end every so often to minimise any electrolytic corrosion due to dampness at any of the cable junctions. This may or may not be the case in Switzerland. – Neil_UK Apr 05 '19 at 14:58

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