DTMF tones not working

[amvubulance]

Hi All

We are running Elastix 2.3.0 32 bit and as of about 2 months ago we started having problems with the DTMF tones. Client phones in, digital receptionist picks up and says "Good Day you have reached Snowball Effect. Press 1 for technical, 2 for sales ..." etc. No matter what button is pressed on the phone, the key pressed does not register. If you however wait till after the IVR recording is finished in most instances you are then able to press the relevant key and go to the department.

Some strange things we have encountered,

A entry level galaxy on the Vodacom network, does not work
A galaxy note on the MTN network gets through without hassles

Swap the sim cards around and the problem migrates with the service provider. Galaxy note with Vodacom doesnt work and the entry level galaxy with MTN does.

We have tested with our upstream trunk provider, as they have a DTMF tester, and it is definately registering the keys, but only with certain cell phones. The problem seems isolated to cell networks, but I cannot say for sure

Is anyone else experiencing this problem? Any ideas of how to fix it?

 

[morkhans]

From your testing it seems then it's not really a Asterisk problem, but rather a provider/interconnect issue.

You should get your trunk provider to take it up with Vodacom or try a different provider and repeat your tests.

 

[Tim the Techxpert]

Hi there Tim here,
I remember that dtmf could be enabled on some phones. Could that info be stored on the sim and moving the sim moves the problem?

 

[InfinityMVS]

1. check what format your SP is sending DTMF tones (default is rfc2833)
2. make sure that rfc2833 is enabled in your peer details of the sip trunk
- dtmfmode=rfc2833 or dtmf=rfc2833

 

[amvubulance]

@morkhans: We contacted our SIP provider and found that they have DTMF tester and from the different networks they also experienced the same issue.

@InfinityMVS: it is rfc2833 and it is definitely in our trunk.

Mailed the ISPA list and got a few valuable replies, would suggest that everyone registers for it. Amazing help from the other providers, even guys willing it give us free test trunks, when our current provider is not willing to even provide this for mere testing purposes.

Will see where this goes, still alot to test.

 

[gmza]

amvubulance:

I'm a bit bewildered by your comment "our current provider is not willing to even provide this for mere testing purposes." When did you ask me to provide you with a second trunk?

May I remind you that:
1. Even when you phoned after 7pm in the evening, I spent 45 minutes on the line assisting you (or perhaps it was your colleague) with this particular problem.
2. You are currently using IAX2 protocol, not SIP, and have neglected to mention that here, despite me going to great lengths to explain that "dtmfmode=rfc2833" is a SIP-specific setting in Asterisk, not an IAX2 setting.
3. Your are not fairly representing things when you state that your provider experiences the same issue with their DTMF test facility, because the issue I identified was specifically with calls from MTN to the facility within the first 30 seconds of the call, whereas you have no problems from MTN at all, only from Vodacom. That was clearly detailed in an email as well where I requested further test results to ascertain if, indeed, this was definitely network (Vodacom) specific.

For the record, I have identified why MTN calls to the DTMF facility did not pick up media in the first 30 seconds; this relates to the fact that MTN's firewall listens for RTP from the remote end first before passing through RTP from their side. When I adjusted the facility to simply play a brief welcome message before listening out for DTMF (as opposed to playing no audio and just listening for it), the DTMF tests from MTN worked perfectly, exactly as from Telkom, Vodacom and Cell C. The issue described here could NEVER have affected you because your systems always played a welcome greeting before listening for DTMF. The MTN issue can only occur in the specific and extremely unusual circumstance where you transmit no audio at all but expect to hear audio from the remote MTN phone first. Even transmitting recorded silence (as opposed to no audio at all) would work around it.

With that out of the way, I can demonstrate, both through my DTMF test application and through other setups where we have delivered calls from our systems to IAX2 and SIP terminated destinations, that the DTMF is working from all the major networks (Telkom, MTN, Vodacom and Cell C) as well as on-network.

But then you know that already because you tested, from the same mobile that was resulting in a DTMF issue on your IVR, towards our IVR, and it worked with our IVR.

You are more than welcome to change over from IAX2 to SIP to see if you get different results, taking into account, once again, that RFC2833 is a mechanism for delivery of DTMF within RTP streams associated with SIP-signalled calls and that RFC2833 has no relevence in the context of IAX2 (which has its own DTMF relay design within the protocol).

Please can you give us an update on what you have found because, right now, as I test from both Vodacom and MTN, using both a Samsung Galaxy S2 handset and a Nokia E51 handset, it appears to be working 100% and your IVR does jump to voicemail when I hit the '9' button. Did you change something on your side?

Please, before suggesting that your provider is unwilling to help, take into account the literally hours of time I have already spent assisting with this problem, making test calls from Telkom, MTN, Vodacom, Cell C and on-network using different makes of handset to your reception number, because it is extremely disheartening for me, after dedicating that much time and putting in the effort to assist you guys, to read those sorts of comments and to have to then respond on a public forum.

Unrelated to this, but the ISPA list to which you refer is restricted to ISPA members and it is therefore not possible for everyone on this forum to subscribe to it. The reason for that is that it is not actually a technical list, although admittedly there are some very smart technical people subscribed to it!