DTMF issue with external IVR & voicemail

Hi guys,

I have a small but horribly annoying problem;

In the UK the only consistant setting for DTMF is INBAND which is fine, however if I set my phones to use that I am unable to access the Asterisk voicemail, if I set the phone to use INFO then I can’t access external IVR’s options. If I set to INBAND+INFO then often (too often) either the external IVR doesn’t accept the key press, either reporting that the number selected is not a valid option or it totally ignores the tone completely.

The only solution I can see is to get asterisk to accept INBAND to access the voicemail system, is this possible and if so where would I change those settings.

Many thanks


Country shouldn’t make a difference. What matters is the capabilities of the device that does the SIP to PSTN conversion.

INFO is obsolete. RFC 2833 is the preferred method.

In band will only work with G.711 (A-law and Mu-Law) codecs.

Hi david55,

Yes I understand about inband only working with inband, and have got my phones & asterisk server to only allow alaw&ulaw.

My problem is that asterisk refuses to understand the dtmf unless the setting is either INFO or INBAND+INFO.

If I set the phones to use RFC 2833 not all the external ivr’s accept the tones and asterisk doesn’t understand the tones either.


SOLVED :smile:

It was an issue with my SIP provider they weren’t doing something correctly, they are now :smile: The way I tested it & proved it was, I rang an external IVR from my mobile and it worked, set up a DISA using my mobile phone and rang the same IVR and it failed. So it wasn’t a phone issue on my system. I then got one of SIP providers staff to ring the same number and they couldn’t work that IVR either (they use the same system as me). After this they soon fixed the issue.