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Thread: Extremely weird problem

  1. #1

    Question Extremely weird problem

    16xi3 1 ISDN line for incoming calls (2 channels)
    1 ISDN line for outgoing calls (2 channels)

    firmware - 4.1.52

    * The receptionist for the last couple of months has been complaining that sometimes she can hear 'ringing' while speaking to a client on the call. We don't think the remote party can hear the ringing, she says the ringing sounds like an old fashion telephone, its loud and makes the call difficult for the receptionist.

    * It is intermittent, and doesn't happen all the time, it can occur at anytime during the call.

    * She has experienced it while talking to an internal extension, the other extension didn't hear the 'ringing'

    * We have tried replacing the Snom-360 (7.1.30)

    We think that the ringing happens when the other ISDN line initiates a call at the same time. However the other ISDN is on a separate line so is highly unlikely to be interfering (at least at the telecom end)

    * Its only started happening in the last couple of months the box has been deployed since October last year.

    We have logged a TSS ticket with Epygi, has anyone else had this problem with ISDN, and could possibly shed some light on this problem?


  2. #2


    The problem was caused by "Generate Progress tone on IP" option in the Advanced ISDN Settings page. The option was enabled on the problematic Quadro, while it is disabled in default configuration.

  3. #3

    Smile Thanks Aramk

    We are not sure how this setting got turned on but turning it off seems to have resolved the problem. Do you know what 'Generate Progress tone on IP' actually does?


  4. #4


    As far as I know this option was implemented to support a compatibility with some special ISDN-PBXs. It is designed to generate a progress tone to the caller during the call establishment period, otherwise there will be a silence only instead of ringback tones, because of ISDN-PBX's specifics. We do not recommend to use this option for general cases. There is another option ("Bearer Establishment Procedure") to solve the ringback problems with ISDN provider, that worth to tune first, before using "Generate Progress tone on IP" option, but this is not your case. Also, we had a small issue with generated progress tone by this option, that the tone wasn't cleared from the ISDN channel and sometimes was playing to the next caller. It is fixed already and will be included into the upcoming releases.

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