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3CX Phone System With ThinkTel VOIP Provider DTMF Signals

3CX Phone System With ThinkTel VOIP Provider DTMF Signals

3CX Phone System With ThinkTel VOIP Provider DTMF Signals

Hi All,

I'm having a strange issue with my 3CX phone system. I have certain numbers I call (mostly 1-800, 1-877), that are hit or miss when it comes to receiving the DTMF dial tone signals. Sometimes they work and sometimes they don't. I really can't seem to consistently create the problem one way or another. It just either works or it doesn't. There is one number (secondary VOIP provider (1-877) that seems to never accept my DTMF dial tone responses.

Basically its just a big pain because there have been times where I gave up after trying to call 8 times and just used my cell phone instead.

We are using Cisco SPA514G phones mostly. We have a few other models but it happens with them as well. 3CX support asked for Wireshark captures and they said the DTMF signals are being sent from the server. Which by the way is just a Windows 2008 R2 server box with the 3CX software installed on it. Basically acting as our internal PBX system.

Our VOIP provider is Thinktel which is pretty large up in Canada. We do have a Cisco 1811 Router in place. We also have 2 ISP's (ADSL and CABLE), all traffic goes out CABLE except the traffic being generated by the server with 3CX software installed. That goes out the ADSL only.

Any ideas why this may be happening? I can't find any settings in the management side of 3CX. HELP me please!!

Thank you!

RE: 3CX Phone System With ThinkTel VOIP Provider DTMF Signals

I only ever use 3CX as a test bed, but how is it set to send DTMF and what does the carrier excpect? Been a while since I've used it but try lloking for DTMF seetings.
You tend to have:
In the Info message

If in doubt, i'd set to RFC2833.

Robert Wilensky:
We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true.


RE: 3CX Phone System With ThinkTel VOIP Provider DTMF Signals

The Carrier (Thinktel) asks me to set up DTMF Tx method as RFC2833 or outband. However, I cannot see any setting in 3CX management side of things where there is a setting for that. This is version 11 of 3CX the latest service packs completely up to date.

The only area where I have a DTMF Tx method is on the phone management screen. If I browse to the IP of my Cisco SPA514G phone I can find a DTMF Tx method but there is no option for outband or RFC2833. I have tried the other options such as INFO and AUTO but they too do not work.

Thank you,

RE: 3CX Phone System With ThinkTel VOIP Provider DTMF Signals

Hey Guys,

I appreciate all your help/suggestions on this case. It seems like it was a case of improper NAT being done by the Cisco router we have. Thintel was expecting a certain source IP for our RTP packets but for some odd reason about 95% of the packets would NAT correctly and the other 5% including the DTMF tones were sent with a different source IP and hence dropped by Thintel.

Strange issue as the creation of it was difficult and not consistent at all for the most part. But we got it all sorted out nonetheless.

Thank you, all.

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