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DTMF Over SIP

Loui

January 26, 2021 17:08

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Having problem when dialling DTMF over SIP. I ring external number who has auto attendant (the remote is not a yeastar system) I get options press 1, 2 etc. On pressing digits nothing happens.

I have listened to the call and there is no DTMF tone on the call.

I have made calls from SIp deskphone, Linkus App on Iphone and Linkus app on laptop.

I also tried changing the DTMF options for the trunk.

I then registered the SIP trunk to a different system (not yeastar) made the same call and that worked ok

 

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2 comments

• 0
  
  Craig January 27, 2021 00:41

  Hi Loui,

  I would be looking at getting a trace via the maintenance - troubleshooting to start. Once you start it, replicate the issue again, terminate the call, then press stop and download.

  The PBX needs to understand DTMF based on the country code and DTMF type (RFC2833, inband/passthrough) and codec.

  If the codec is a narrow bandwidth, such as G729 (which you can see being negotiated in the SIP SDP), then try changing it to Alaw (g711a) or Ulaw (g711u). 

  It sounds as if the difference is that the other system negotiates different codecs, but the trace will provide information on that.

  If you know how to read packet traces, you will be looking for a DTMF payload. For example, if you press the 1 digit, you will see this 4-5 times (depending on the payload).

   

  Frame 686: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
  Linux cooked capture v1
  Internet Protocol Version 4, Src: 192.168.6.11, Dst: 192.168.6.150
  User Datagram Protocol, Src Port: 10008, Dst Port: 11356
  Real-Time Transport Protocol
  RFC 2833 RTP Event
  Event ID: DTMF One 1 (1)
  0... .... = End of Event: False
  .0.. .... = Reserved: False
  ..00 1010 = Volume: 10
  Event Duration: 0
  VSS Monitoring Ethernet trailer, Source Port: 0

  The above means that the PBX was able to successfully read the digit "1".

   

• 0
  
  M. Asghar Perwaiz August 02, 2021 10:25

  you can try to change the DTMF payload 97 or 101