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Topic # 15032 31-Jul-2007 22:40
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Hi,

I am having huge difficulties with dtmf tones not being recognised when trying to access my voice portal from the phone connected to a linksys PAP2T.

What happens is - I call the voice portal and I am asked for the passcode anything I enter is not recognised i.e. it is as though I haven't pressed any keys at all, there is a long pause after I press the hash key and then I get this code is invalid.

I changed the settings on the web portal to not require login from my own phone, but now even though I don't get asked for a passcode when I press a key for an option e.g. 8 to change the passcode again the dtmf tone is not recognised long delay then repeated message.

I have contacted WxC about the issue and even though they have been very helpful they have not solved the problem.

They did send me a replacement PAP2T which I connected and still have the same problem. I have also tried different phones. I have tried different cables going from PAP2T to phone.

I am connecting to a router connected to a paradise cable modem.

If I dial **** I get the Sipura voice configuration prompt no problem and I can enter options to find out settings, etc. So it seems that the phone DTMF works and the Linksys PAP2T understands the tones OK, it's just the VXF voice portal doesn't recognise the tones being sent to it. I personally think it has to be something at the WxC end. The number I am using on the line1 is a ported number, nothing on line 2.

Please help - my wife thinks I'm a fool, hey, what's new! Anyone had the same problem?




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26 posts

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  Reply # 80659 31-Jul-2007 23:12
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Hi Brewer,

Are you able to make voice calls without any issue? You can hear the remote party and they can hear you?

My first thought while reading your description is that its not just a problem with DTMF but in fact your whole RTP stream (Voice + DTMF) isn't reaching the remote end. Which could be caused by a firewall blocking outbound traffic or funky routing tables.

But, I'm sure it wouldn't be anything like that if WxC have had to send you a new device.

Keep us posted! :-)


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  Reply # 80679 1-Aug-2007 07:49
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This issue is we are not seeing the DTMF, the unit you have been sent was actually preconfigured and tested here prior to being sent to you, this worked the portal is accessed correctly with no problems,

at this stage one of my team is working with you on this and will continue to do so untill we find the issue, and yes you are the only person we have seen with this issue to date, henec the reason we wanted to replace the device with a known good one.





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  Reply # 80683 1-Aug-2007 08:00
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Have you tried a different brand of phone at all? Does the problem still occur?




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  Reply # 80686 1-Aug-2007 08:26
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Thanks for the responses.

I can hear voice fine and every other function/feature is working OK. I have tried a variety of phones with no joy.

Maverick, I don't want to seem ungrateful for your teams help, it has been fantastic, I'm just trying to get more information myself to help solve my problem.

I have done a pretty good google search and have found similar issue with PAP2 NA device where the DTMF setting was changed from AUTO to INBAND to fix the problem. Also some discussion about increasing the DTMF volume and duration.

I have tried 2 separate cables from PAP2T to phone but will buy another today and check it also.

One of the reasons I believe this is related to the ported number is because when the device was originally connected I had 2 lines - line 1 was the WxC number 04831.... and line 2 was my ported number. I wasn't interested in the WxC number so connected phone to the line 2 only. At this stage I had the DTMF tone issue. When I tried connecting my phone to line 1 it appeared to work fine ringing the portal and I had no DTMF issue at all. I then got the WxC number disconnected and the ported number changed from line 2 to line 1, it still has the problem.

This showed that the phone was OK, the cable was OK, the device was OK, the WxC number was OK, the voice portal was OK. The only thing that wasn't OK was the ported number line. I don't know how this can be except for a configuration setting at WxC end.

Thanks again.



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  Reply # 80693 1-Aug-2007 09:00
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... or your phone went faulty and that is now the problem.  Can be as simple as one of the kids dropped the phone without you knowing it (or the dog or wife or partner, whichever is applicable).




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  Reply # 80696 1-Aug-2007 09:16
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Brewer,

As you've noticed, DTMF in VoIP is a very fragile beast.  It's essentially the same problem that people have getting fax machines and modems to work with VoIP lines.  If it is left undetected by the endpoint, it is likely to be mangled by the codec in the device and not make it to the far end to be detected (if it's configured to detect it at all).  Usually, the endpoint will detect the dtmf and create events that replace the DTMF tone packets in the data stream.  These are then either re-generated by the PSTN gateway or understood by the other VoIP endpoint.

In H.323 there were at least 3 different ways that DTMF could be transported. :)  It looks like there are several in SIP land too.

The options for the Sipura (PAP2) are:
INBAND - Undetected by the endpoint.  Definitely the wrong choice.  You're one codec choice/jitter/dropped packet away from losing your DTMF.  Frustrating.
INFO - It's sent in a SIP event on the call signalling channel.  Probably not the right thing to do, it can result in wierd race conditions between the DTMF tone and your speech.  Although, it's the only thing you can use if you want DTMF, but not the entire speech data.
AVT - Convert the DTMF into events in the RTP stream.  This is what you want to happen.
AUTO - The endpoint will choose INBAND/AVT based on codec choice and negotiation with the other end.  Probably the wrong thing to do, letting the endpoint choose is usually bad.  They make the oddest choices sometimes.

So, I've seen this fail in the following situations:

1) There is a poorly configured VoIP-POTS gateway in the middle of the route, which results in the DTMF being stripped.
2) The DTMF is undetected by the endpoint, resulting in the codec mangling it to undetectability.
3) The endpoints don't understand the same method of DTMF encoding (INFO vs AVT)
4) The user isn't pressing the button for long enough. (yes, it's true!  Weather presenters are the worst for this) - more of a problem with INBAND.

I've also found some manuals for the endpoints.
http://wiki.pbxnsip.com/index.php/Linksys
http://www.sipura.com/Documents/SPA941AdminGuide.pdf
http://www.sipura.com/Documents/SipuraSPAUserGuidev2.0.9.pdf

Oh, and flash hook (quickly pressing the button to hang up the call), is handled the same way, with the same problems. :)

Sorry, I couldn't resist jumping in.  I've had lots of fun with DTMF in the past. :)

Maverick's got a good crew, let us know what the result was.  I'm always interested in this sort of "gotcha".




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  Reply # 80699 1-Aug-2007 09:38
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Hi Phil,

One of my customers has experienced this issue too. I haven't raised it yet as they are also having major ADSL issues, so are trying to get that resolved first. They make a lot of conference calls, i.e. will dial an 0800 number, then enter a series of *nnnnnn* codes etc to access their conference. Often have to enter these several times before successful.

Thanks




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  Reply # 82183 13-Aug-2007 14:02
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Brewer, did they get your dtmf problem sorted out?  I'm interested in what was wrong and what the solution was.  I've got an alarm tech coming out next week to see if we can get my alarm working, and I'm wondering if it's the DTMF being mangled by the endpoint.

Thanks!






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  Reply # 82187 13-Aug-2007 14:11
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No, unfortunately no solution yet.

They have offered to send down the phone and cable that worked for them on the PAP2T device they have sent. I doubt this will solve the problem as I have tried numerous phones and cables already.

I want to try a different router off the cable modem to see if something is being blocked by the router. Other than that, it looks like I am screwed.

One point to note though was I think I may have been incorrect when I said that previously it had worked OK on one line and not the other. They have set the device back to have two lines and neither of them work.

Cheers.

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  Reply # 82203 13-Aug-2007 15:52
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jpollock: Brewer, did they get your dtmf problem sorted out?  I'm interested in what was wrong and what the solution was.  I've got an alarm tech coming out next week to see if we can get my alarm working, and I'm wondering if it's the DTMF being mangled by the endpoint.

Thanks!


Try fitting an ADSL line filter between the alarm dialler and the VFX port.  Not for filtering out ADSL signals, but rather simply as a low pass filter to limit the bandwidth of the dialler.  Diallers assume you connect to a limited badnwidth analogue phone line and do not filter very well.  This trick worked for me for a modem on VFX, never have any problems with it.




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aw

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  Reply # 82309 14-Aug-2007 10:54
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What happens when you take your PAP2T to a friend's place  either nearby or across town (or both) (assuming they have decent broadband) and try it there?



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  Reply # 82403 14-Aug-2007 21:15
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I have finally found the answer to this problem. Having tried different phones, lines and PAP2T devices I replaced the router - Dick Smith XH6833 with a new router and the DTMF tones are now recognised.

Even though the router was cheap it was reliable and hadn't had any issues with other services previously. One for WxC to take note of for future customers with similar issues.

Thanks for everyone's help.

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  Reply # 82435 15-Aug-2007 05:44
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Thanks for the info Robert,

Yes one to take note off as we had not seen this before and it is actaully strange to see the router block the method we are using for DTMF, somewhat of a "Gotya" I think, We will see if we can look at this particular router and also make a note of this issue with this particular router.




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