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Department of Informatics - Communication Systems Group


This page will get updated continuously as problems occur and are reported. If the problem's likely to happen to somebody else, it'll appear here. The page itself might be replaced by a Wiki for users to help each other, if this appears sensible at any later time (opinions welcome).

  • I am trying to host a conference, but one of participants is unable to join. He always receives the answer that the conference number is invalid...
    It is likely that the person's phone system is blocking outgoing DTMF (dialtone) signals, making it impossible for the person to enter the conference number. (Therefore he always receives said answer after a timeout) Please consult the 'Frequently Asked Questions' section for a solution.
  • I'm using XLite 2.0 under Linux and sometimes after a call, sound crashes and won't work anymore, until the program has been restarted...
    Apparently this happens, when XLite sometimes doesn't get the information about the hangup from the other side. Try to make sure that after a call XLite ends up in 'Hungup' state and the line is no longer indicated as being used.
  • My Nokia E70/N95/... won't register with the IFI VoIP Server...
    There are a couple of catches with the Nokia VoIP Client configuration: For instance the login information should be entered in the 'proxy server' part and not in the 'registry server' part, and the realm (which might eventually be reconfigured to '' on our behalf) setting should be 'asterisk'... more information (a.o.) here, or by searching google (Nokia N61 asterisk)
  • I've configured my account to ring at an external PSTN phone number (e.g. my cell phone) when I'm called... but it won't work...
    At the moment, an additional prepended '0' is required for this to work with external PSTN numbers (see 'Issues' page). This will eventually change, when this issue is solved.
  • My calls are being dropped after a short time of conversation.
    Check your VoIP client configuration for automatic disconnection. In X-Lite for Windows, for example, make sure the check box shown below is unchecked in the Options window, under Network, Call Inactivity. The software may disconnect your call even if there is activity.

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