no Alerting / Ringing Tone in SIP to ISDN Calls

Owned by Christian Richter
Apr 12, 2019
2 min read

Problem

The Caller hears no Ringing or Alerting Tone when he calls from SIP to ISDN. After the Call has been connected audio works fine though. 

The pcap trace shows that both a 183 and aftwards a 180 Status message was sent to the SIP side, because the ISDN Side has sent a Proceeding → 183 and later an Alerting → 180. 

Solution

Some Providers don't create inband Ring tones when they receive a 183 Message. The behaviour of the gateway can be modified so that the 183 is not created and the ISDN Proceeding is ignored. 

1. Create a Call Progress Table with direction SIP-ISDN: 

2.Create an Entry which lets the Gateway Ignore Proceeding messages:

3. In the SIP - ISDN Dialplan Rule click on "more": 

4. Add the following manual configuration option, so that the previously created call-progress table applies for this dialplan rule:

5. finally click on ACTIVATE and try again.



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