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DTMF tones not functioning on three party conference

Medium Priority
Last Modified: 2012-05-06
I have come across this scenario in the testing of an IVR solution I've developed.  I don't actually expect to be able to fix this, but I'm looking for some insight into what's happening that might help me to figure a work around.

I've discovered that when a caller has initiated a three-party-conference they are not able to send DTMF tones.  Scenario is:
Person A makes call to Person B
Person A conferences call with IVR C
If Person A presses keys, DTMF tones are not heard or detected
If Person B presses keys, DTMF tones ARE heard on all calls and detected by IVR

I've tried permutations of this such
Person B calls Person A
Person A conferences call with IVR C  but again
If Person A presses keys, DTMF tones are not heard or detected
If Person B presses keys, DTMF tones ARE heard on all calls and detected by IVR

It always seems to be that the caller who initiates the conference is unable to send DTMF.  I've tested with different phones and different IVRs, same story.

Can anyone explain what is going on here?
Watch Question

Depending upon the switching system that is handling the conference, this might be a "working as designed" problem.  Some systems allow for a three party conference (originator and two others) but then disables the DTMF pad until conference is completed.  The end party is only connected to one source, so that key pad is still able to generate tones.  
It is not a problem with the IVR.
On some systems (like the old Toshiba key systems) you had to first press the * and then the # keys before the touch pad tones would be generated.  
What is the device used for the conference?

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That's very interesting to know, thanks for the info.

I'd tested this with a few different devices specifically initiating the conference from a Blackberry, an I-Phone and a standard fixed-line desk phone.  I just had a go at pressing * and # but this did not activate the DTMF.

I've reworked the solution so that the conference initiator doesn't need to enter DTMF as I don't think there's much I can do about this one.

I appreciate your help - thank you!

Actually, I'm facing the same problem. I have two vxml applications, say B and C. I'm the caller, A. One of my VXML applications will play the DTMF tones and the other VXML application will have to receive this tone and respond to this. This is how I try to accomplish this.

I Have a XLite phone. I call to the IVR B, first. Once it is connected, I dial to IVR C. Now i establish a conference. So there are now 3 parties in the conference. (Myself, IVR B and IVR C).

When IVR B plays the DTMF tone, IVR C is not able to recognize that. It doesn't even listen to that. But when I press some Key from my phone, it is recognized by IVR C. I dont know what is the issue. Please let me know how to solve this problem.
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