Wrong DTMF inputs received by asterisk 11.16

Hi, have been scratching my head over a wired issue that I encountered recently
System details
OS - CentOS6
Asterisk 11.16
Using sangoma cards A104 & A108 connected to PRI Lines

Issue - When a caller from a GSM network calls the DID he is presented with an IVR in which he/she can choose from 1-6 options which is presented by the IVR
Now when I check the asterisk logs, I spot that the Asterisk is detecting DTMF inputs like DTMF:A, DTMF:A12, DTMF:A155

Though in my research I found that DTMF inputs can be A,B,C,D along with normal inputs 1-9,0,*,#.
Now since the call is from a GSM network a user does not have the option of DTMF inputs A,B,C,D in a GSM phone. Then how the asterisk is detecting such inputs?
Also the weird DTMF inputs will always be DTMF:A not B,C&D.

Because of these weird DTMF inputs the system detects and invalid key pressed and the call is failed.
Please help me with this issue or at least point me in the right direction.
Can this be a operator related issue which I doubt.?

I’d be surprised if the GSM air interface didn’t allow A, B, C, and D digits.

For the Sangoma card, please contact Sangoma.

However, used correctly, GSM sends digits in the signalling channel, and the actual tones are generated in the base station,because the GSM codec is not designed for artificial tone pairs. As a result, the first question would be whether these tones are being sent, correctly, in the above way, or whether they are, somehow, being sent in band, in which case reliable detection is unlikely.

Next. I assume that the PRI is using A- or Mu-Law and that you are not trying to force it to transcode to anything else, as those are the only codecs really suited to in band DTMF.

Other things to check are whether the uplink is silent or, at least, a DTMF friendly tone,as near end cross talk could produce false detections.

If none of that helps, you will need to capture the raw media stream. I’d suggest using the Record application in .slin format. Once you have the raw stream, you can use various tools to get a spectrum from it, to see if you are actually receiving a clean DTMF tone pair.

From a quick look at ftp://ftp.sangoma.com/WINDOWS/AFT/Windows_API.pdf it would seem that those cards may be able to do their own DTMF detection. If you are using that feature, only Sangoma can help you.

Of course, in a quick skim, it is difficult to distinguish between features implemented by the driver and those implemented in the hardware.

Also note that Asterisk 11 is in the security fixes only phase of its lifecycle, and will reach end of life in October.

Thanks David for such a quick response.
In the cards I have enabled hardware DTMF detection and you are right its an E1 pri with A-Law and I am not doing any transcoding.
Probably the right way to go is to contact sangoma as DTMF is being detected by the cards. Will also check with the operator if the DTMF is being sent inband or otherwise.
Also I do know that the Asterisk v11 is reaching the end of life in October but there is a saying “If it ain’t broke, don’t fix it” so till its working will be using v11, in the mean time will test will newer versions of asterisk if it will be compatible with the environment that we have created.
Thanks again for pointing me in the right direction.