Overlap SIP dialing

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Asterisk Users 4 Comments

Looking at the history of the list I don’t expect any answer but lets
try anyway:

Does anybody use overlap dialing from SIP devices to asterisk? Does
anybody have a working example?

4 thoughts on - Overlap SIP dialing

  • 7 sep 2011 kl. 15:59 skrev Daniel Tryba:

    To add to your question: Does anyone have a phone that supports this properly?


  • Unless I’m mis-remembering, this was the point of adding the ‘!’
    dialplan match character. If you use _X!, and you have your SIP
    endpoints configured to send an INVITE as soon as the user has entered
    two digits (and you have no other patterns in the context that could
    match), then the dialplan will match against that and initiate a Dial()
    on your ISDN PRI. Since the number is not yet complete, the SETUP
    message on the PRI won’t result in the call proceeding, and as the user
    of the phone presses additional digits they’ll be sent to Asterisk as
    DTMF, bridged over to chan_dahdi, and it will send them as INFORMATION
    messages rather than as DTMF digits, because it knows the outbound call
    is still in ‘dialing’ state.

    However, this is still going to ‘mess with CDRs’ as you put it, because
    the only switch in the network that knows the complete number that was
    dialed is the PSTN switch that your PRI is connected to. It seems
    possible that chan_dahdi could ‘update’ the EXTEN on the current channel
    as the additional digits are dialed so that the CDR contains the
    complete number, but I have no idea whether it does or not.

  • OK, yes, I can see how this would occur. Explicit Answer() (or even
    Progress()) before Dial() would resolve that problem, but makes the CDR
    situation even worse.

    Honestly, I’m not really sure that there is a practical solution here.
    ISDN overlap dialing was intended for ‘dumb’ phones, and SIP phones
    aren’t ‘dumb’ 🙂

  • My quest for overlap dialing started with the request to create a
    transparant SIP connection to a ISDN BRI PBX without adding unnecessary
    waiting for timeouts on the side of the SIP gateway to get all digits to
    send them en-block to Asterisk. My feedback for this request to the
    customer will be:
    -just use en-block dialing
    -terminate the dialed number with # when not using en-block dialing
    And make sure to strip # from en-block numbers 🙂

    But I’m willing to give up now I see that this will not work with
    billing anyway.

    Thanks for the feedback and hopefully other people wanting to do overlap
    dialing will find this thread and may take it into account.