Asterisk Plays Tone in the middle of a call

Hello All,

Im a sys admin for my company and have recently taken on the phone systems. We are having an issue where the server will play back a touch tone in the middle of a call and once it starts it will not stop until the call is ended.

There is nothing in the logs to indicate a key press or error that would cause the tone.

Can someone set me the correct direction so that i can remedy this issue.

Thanks for the help.



What version of asterisk , What Handsets and what are the Co lines,
This is a known issue on some systems.


snom handsets
Vitelity provider

where can i find info about this potential issue.

JFYI (no thread-jack intended) I have a very similar problem.

Asterisk 1.4.22 - various SIP hard phones (eg. ATL , Aastra, Gransdtream, Polycome etc etc).

About 20 seconds (or so) in to the call a single DTMF tone is heard at our end (ie. the person on the SIP handset). This isn’t heard by the other party (caller or callee). Sometimes we don’t get the tone - just a slight pause (like a silent tone).

I did notice an event in the AMI when this happens. I got an ‘Unlink’ event immediately followed by a ‘Link’ event for the same call.

If you have something that can monitor the AMI - see if you get the same ‘Unlink/Link’ event when it happens.

In the meantime - I’ll see if I can sort my problem out - and keep you informed.


I’ve seen this before with Sipgate and the problem was due to an incorrect dtmfmode setting on the trunk.

It may be worth trying different settings? (


Sorry to jump in again - but I’ve tried them all Matt (phone and Asterisk) and it still happens shrug.

Thanks for the input though :smiley:.