Why is there and interference between DSL and phone?

roni June 11, 2011
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If my phone is plugged in with a filter I get no internet and my answering machine on the phone will not work. If I take filter off, I have phone and answering machine, but no internet. If I switch phones, the phone works and internet works, but I don’t have answering machine.

  1. Mike
    June 12, 2011 at 8:35 am

    This is definitely something you should contact the technical support about!

    There are various scenarios how things have to be setup depending on the general infrastructure by your Service Provider and your in-house cabling:
    - multiple filters/splitters between every socket and device- single filter/splitter after the primary socket in front of the modem
    - single filter/splitter after the primary socket in front of the telephone
    - single filter/splitter after the primary socket which has one phone and one modem connector
    - single filter/splitter before the primary socket from which you go to modem and telephone

    Theoretically you don't need any filter/splitter for ADSL to work. But depending on the frequencies used you might get interference within your telephone or dropped connections on your modem.

    In my place the general setup is that you got one primary TAE socket where the line connects to. In this socket the signal is bridged between the A and B connectors.
    The A socket/connector goes to the splitter and from there into the modem. The B socket/connectors goes directly into the telephone.

  2. Anonymous
    June 11, 2011 at 6:34 pm

    The filter should be on the line to the phone.

    What happens without the filter depends on the phone. Sometimes when the phone rings the internet drops out, sometimes the internet just wont connect. Often the phone is hissy without the filter.The filters protect from crosstalk between the telephone and DSL line which will adversly affect the signals.

    Some modems will interfere with the phone line more than others.  just leakage of the DSL signal into
    the audible band of the phone line. Different phones have different frequency
    responses, so changing phones can make the DSL signal more/less obvious.


  3. Oron Joffe
    June 11, 2011 at 4:14 pm

    Faulty microfilter! Note that you must have a microfilter on every socket in use, even if there's just a phone plugged into it.