[VoiceOps] AT&T Cellular - DTMF

Adam Vocks Adam.Vocks at cticomputers.com
Thu Jun 25 09:45:40 EDT 2015

Just found out today that it only seems to be happening from certain cellular towers.  Someone sent me the ATT-M NOC phone number, so wish me luck!


Thanks for all of your replies.




From: VoiceOps [mailto:voiceops-bounces at voiceops.org] On Behalf Of Adam Vocks
Sent: Wednesday, June 24, 2015 12:24 PM
To: Paul Timmins
Cc: voiceops at voiceops.org
Subject: Re: [VoiceOps] AT&T Cellular - DTMF


Thanks Paul,  I forgot to mention that we have no trouble with audio.  The audio is good in both directions for the entire length of the call.


From: Paul Timmins [mailto:paul at timmins.net] 
Sent: Wednesday, June 24, 2015 12:08 PM
To: Adam Vocks
Cc: voiceops at voiceops.org
Subject: Re: [VoiceOps] AT&T Cellular - DTMF


AT&T doesn't (reliably) pass two way audio until the call supervises. I had a customer with this issue before and they were sending a proceeding (technically a 183 with SDP because they were SIP) and playing a menu recording, and not sending the supervisory message (in their case a 200 ok) until they pressed a key. This worked with every cell phone except AT&T (and of course that was my fault). I set my system to answer calls via a feature server then ring it into them, and that fixed it, and then I called their vendor to the mat for doing things that way. They fixed it and the issue was resolved.


On Wed, 06/24/2015 12:57 PM, Adam Vocks <Adam.Vocks at cticomputers.com> wrote:

I’ve got an odd problem that someone might be able to point me in the right direction to get some help.


AT&T cellular customer calls a number destined to our LRN.  Customer presses a digit on the phone, no DTMF audio ever comes across the trunk.  If that same customer calls a number with the same npa/nxx not destined for our LRN, DTMF audio comes across the trunk.  These calls are coming to us via SS7 trunks and the ILEC that these calls transit through has verified that both calls come in on the same trunks, one has DTMF audio, one does not.


This problem started on Thursday morning.  Prior to Thursday morning, AT&T cellular calls were arriving to us via our FGD Tandem connection, now they are arriving via the local rate center switch.


I’ve talked to AT&T and attempted to put in a ticket on the DS3 that enters the ILEC, but they refused to do that because they said the DTMF would be audio and they would just pass it through.


Anyone have advice?


AT&T (low level tech) states that the DTMF tones are generated at the phone and are in the audio stream the entire way.  Does anyone know if AT&T uses some sort out of band dtmf signaling?




Adam Vocks

CTI Fiber 

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