[Asterisk-Users] Re: Beeps during Sip to Sip phone calls

[Rich Adamson]

> >> Yep, I've seen it and from reading http://www.voxilla.com it's a
> >> pretty common problem.
> >> 
> >> If you turn on debugging what you'll see is that the Sipura has
> >> mistakenly detected a DTMF code in the audio stream and is relaying it
> >> by repeating the signal (very loudly I might add)
> >> 
> >> So this appears to be a bug in the most current firmware. I've
> >> reported it to Sipura including the debug output. Maybe more people
> >> should do the same.
> >
> >You'd think that switching to RFC2833 DTMF would fix that.
> 
> That is actually the problem.  It thinks it hears DTMF so it sends an
> out-of band signal.  The other end receives this and produces the
> audible tone.
> 
> Switching to in-band fixes it.  Well, works around it. :)

I might add that in my spa3k config, incoming pstn calls are sent
directly to the fxs port (with no * involvement). Certain voices
trigger the tones as noted. However, switching to in-band would
obviously not impact the pstn->fxs disturbances. To bad they 
haven't provided some sort of tone detection timer that could
be increased a little to reduce the disturbances.