OK, it looks like my understanding was way off base.

 

On the advice of Dave D., Eric V. and Dave W., I've tried:

-    Locking the phones into G.711

-    Increasing the DTMF On/Off times from 50 to 150 (tested at 25ms
increments)

-    Increased the DTMF level from -15db to -7db

-    Verified that RFC2833Control is enabled

-    Verified that ViaRTP is enabled

-    Verified that RFC2833Payload is set to 101

 

 

I have two Customers, a Vendor, and my home answering machine that I am
using for testing, and I have not been able to find a combination of
these parameters that will get DTMF to work reliably.

 

I also think I got lucky on the day that I made a bunch of test calls
and came up with my estimate that it was working 75% of the time...
I've done more extensive testing since then, and it seems to work
correctly more like 10-20% of the time.  I've probably made 20-30 phone
calls to my test targets just today, and only had a couple successes.

 

 

Mike Burden

Lynk Systems, Inc 

e-mail: [email protected]    

Phone: 616-532-4985

 

 

 

 

From: John Lodden [mailto:[email protected]] 
Sent: Friday, March 05, 2010 3:40 PM
To: Burden, Mike
Subject: Re: [sipx-users] DTMF Issues Revisited

 

Mike,

MNS is a CLEC with Class 4/5 switches (i.e. we can provide dial-tone
just like the LEC).
We don't interface at the FXO/FXS level, we have many hundreds of  DS3
level SS7 trunks into the PSTN.

Most likely the issue is the phone will not send DTMF  until "Connected"
message is sent back from the far side.

-jrl

 


On 3/5/2010 3:27 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?

 

 

 

Mike Burden

Lynk Systems, Inc 

e-mail: [email protected]    

Phone: 616-532-4985

 

 
 
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