On 3/5/2010 2:27 PM, Burden, Mike wrote:
Good afternoon,
Most of the time (about 75%) we can call a Customer/Vendor/etc that
has an automated attendant, and we are able to make selections or
choose extensions using DTMF on the keypad.
Once in a while, though, we make a call and are not able to make a
selection unless we wait until the auto-attendant on the receiving end
finishes its spiel.
Since our configuration isn't changing between calls, and I assume
that our ITSP isn't changing configurations, I believe that DTMF is
configured correctly in sipXecs (or else it wouldn't work right 75% of
the time.)
My theory is that the ITSP must have a number of FXO/FXS devices to
connect VOIP calls into the POTS system. I'm guessing that they may
vary somewhat in the quality of the DTMF tones they generate, and that
different calls being routed to different FXO/FXS devices explains why
sometimes DTMF works fine and sometimes it doesn't.
Could I be onto something here, or is there a flaw in my reasoning?
I can tell you how my ITSP (Verizon) works. When they detect tones like
this, they immediately switch codecs if the call is presently negotiated
to G729. We had to prove our setup supported this renegotiation before
they would certify it.
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