DTMF Talkoff Beep (still)

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Hi all,

I am still receiving reports from some users that calls they make or receive contain loud deafening beeps that can last a couple of seconds. I understand this is DTMF talkoff and is being triggered because the phone interprets speech as a key press (say if someone is pressing 1 at an IVR). Asterisk triggers DTMF emulation when the talkoff duration is less than 80ms, and I
have found a variable in channel.c that I *think* I need to change to make it more tolerant, but it looks like I’ll need to recompile the whole platform from source for it to take effect (how would I do that given I’m using a prepackaged FreepBX distro?)

We are using an FreePBX Asterisk phone system with both SIP in and SIP out trunks for connectivity. My question is how do people running SIP phone systems mitigate against this? I understand Asterisk SIP implementations can be fairly prone to things such as DTMF talkoff. It’s very annoying for the end users.

I have tried a variety of different settings on the phones (Cisco SPA512G), including InBand/OutBand etc, such as the following but without any success
– the users keep reporting the same problem.

Cisco’s InBand/OutBand DTMF implementation/setting doesn’t seem the clearest compared to other phones I’ve deployed.

As always, thoughts appreciated.



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