DTMF not being forwarded by the PBX

Discussion in '3CX Phone System - General' started by ppickens, May 29, 2015.

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  1. ppickens

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    So,

    I've been taking a look at something for a client and found something a little off about their server that I can't quite tell what's going on. In this case, they can dial out, but the external IVRs that they contact are not receiving the DTMF. I ran a packet capture just to be careful not to just pin it on the carrier, and I did run across one curious thing. The PBX is receiving the DTMF on the internal leg, but not sending it out on the external leg of the calls. Has anyone run into this issue before?
     
  2. leejor

    leejor Well-Known Member

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    What type of trunks are you using?

    What DTMF Method you have set in the phones?

    If you use a gateway for trunking, the Method must match in both the set and the gateway, for the gateway to re-generate the DTMF and pass out on the trunks.

    If you use VoIP trunking, then the SIP method must be compatible with your provider.

    http://www.3cx.com/blog/voip-howto/dtmf-rfc2833/
     
  3. ppickens

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    My primary question is not about the gateway or the phone. This is about the server itself. The phones are located locally and they pass the DTMF on to the server without issue. Looking at the external leg to the provider there is none leaving from the PBX at all.

    If I am correct, be it compatible or not, I should be seeing it sent via the packet capture from the server to the provider. If what you pose is correct I would be seeing it sent but audio evidence of the external PBX's IVRs accepting the DTMF via listening to the calls.
     
  4. leejor

    leejor Well-Known Member

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    DTMF is either sent as audio, which can work in some situations, but can depend on the Codec in use. In general it is sent as a message, either RFC2833, or SIP-INFO. Read the Out of Band section in the link I provided. If you are relying on just audio, then your choice of Codec, generally anything other than G711u/a, may be preventing it from getting through.

    You must select an out of band method compatible with your provider, this is done in the set.
     
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