Cisco DTMF relay for outgoing call

Discussion in 'VOIP' started by Tobias Erichsen, Apr 6, 2004.

  1. Hi everyone,

    I've got a small problem concerning Cisco VoIP-GWs in connection
    with DTMF-relay and outgoing calls:

    A H.323 based conferencing-server tries to dial up a peer
    which is located in the pstn / isdn. This works fine. When
    the connection is established, the participant in the pstn/isdn
    is supposed to identify himself with a pin-code using dtmf.

    Unfortunately it seems, that I cannot tell the Cisco gateway
    to relay those dtmfs from the dialed pstn-peer via H245
    alphanumeric to the conference server.

    Does anyone know if there is some kind of tweak to get
    the behaviour?

    Tobias Erichsen, Apr 6, 2004
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  2. Tobias Erichsen

    aal Guest

    hello What is DTMF relay

    aal, Apr 7, 2004
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  3. The detection of DTMFs on the pstn-side and transmittal of those using
    the signalling-channel. This is necessary, as the dtmf-tones will not be
    relayed through the voice-channel correctly when this channel is used
    with a compressed codec like G.729 for example.

    Tobias Erichsen, Apr 7, 2004
  4. Not sure - but you should be able to find the information on enabling DTMF
    relay in the gateway's user's manual. Follow those procedures. If it
    doesn't work, you'll have to contact their tech support and ask.

    As a workaround, G.729 codec actually passes tones (including DTMF digits)
    reasonably well if the sender holds the digit for a bit (say, > 250ms). If
    he's dialing out from a PBX, though, he may not have control over the
    duration of the digits, and they may not get through.

    Good luck

    James Calivar, Apr 8, 2004
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