DTMF inbound and Digital Receptionist

[aznarepse]

Hi all,
I am having some little problems with digital receptionist and DTMF.
I have a Linksys SPA3012 connected to the PSTN line and to a box with 2003 and 3CX. The SPA3012 is registered as ATA and a PSTN device in the 3CX and it generally works fine.
The problem is with the DTMF. When calling externally to the PSTN line, it gets a connection with a digital receptionist or special menu which requests an extension and or password. If I dial manually and slowly the digits, the DR normally gets them all right, although with some problems (I normally have to wait for the digital voice to stop and often repeat the number). However, if I program them in the memory of the phone from which I am calling, the DR just misses them mostly.

In the SPA3012, I have set up the settings, which I believe have an effect over the DTMF, in many different ways, being at the moment after much googleling:

DTMF playback level: 4
DTMF playback lenght: .9
Preferred codec: G711a (in both Line1 and PSTN line)
DTMF Tx Method: Auto (in both Line1 and PSTN line) which according to the manual will select either Inband or AVT (RFC2833) depending on the codec negotiated.
PSTN Dial Digit Len: .2/.1

Has anyone had the same difficulties? Any experience with this setup?
Thank you very much for any help!
All the best,
Adan

 

[abc123]

Can you run a wireshark capture on your 3cx pbx and see what the 3102 is sending.

That way we can see if all the presses are coming through and if so we can tweak the levels for DTMF once we know what is going on.

 

[aznarepse]

Hi Mark,
thank you very much for your response.
I have the capture. There is a broken first tone in a sequence; Shall I upload it here?

Best,
Adan

 

[abc123]

probably best to email it.

pm me for an address to send it to.

 

[mfm]

Hi,

What firmware are you running on the device, also did you factory reset the device prior to setting up ?

 

[aznarepse]

Hi,
I updated the SPA's firmware to 5.1.10(GW) and it was brand new. I set it up as per the instructions in your website. It registered straight away and has given me no problems.

Best,
Adan

 

[leejor]

I was looking into an outgoing DTMF issue last night on an SPA3000, it turned out to be the far end, as a regular phone across the PSTN line would not even work, for the second part of a menu system. Are you finding this to be an issue with more than one destination? Are you using an analog set that puts out very short, fixed duration DTMF tones? If you are using a VoIP set, or even an ATA, the outgoing DTMF method must match that in the gateway. Setting "Auto" , as you've done, should cover all bases.

The setting I had in that unit were Playback Level of -15.0 ( the default is -16.0), yes that is a minus in front. The Playback length set at .2 ( the default is .1) The other settings are set at Auto, (all defaults).
Place a call to a landline or mobile number where you can listen for the tones when you press a key on the 3CX extension set. See if you get the tones at a reasonable length and level.

 

[aznarepse]

Outgoing DTMF are reasonably good (not infallible though). I have an analogue phone attached to the SPA unit. My problem though is when I call to my own phone number, for instance with my mobile. The DR on 3cx misses the DTMF quite often.

To be honest, I am not sure what playback level and length settings do and the manual is not clear at all. I have looked a lot on forums and it seems that the settings by default are far to low. Anyway, it seems to affect the FXS port on local. "Local DTMF playback level in dBm, up to one decimal place."

I am not sure as to how the flow of DTMF works when I call to my number and establish a connection with the gateway and 3cx. I generate the DTMF from a remote location, for instance my mobile, and I those tones are being carried (not sure by which method; I guess out-of-band at least until it reaches the operator, for it works with GSM codec) through the PSTN line until the SPA gateway, which I am not certain if it interprets them and replay them or if it just lets them through transparently towards the 3cx.

 

[leejor]

I was under the impression that you were having issues calling external numbers from a 3CX extension through the 3102. The DTMF settings will not affect incoming DTMF if your problem is getting the 3CX DR to recognise DTMF sent from your mobile. This has come up in the past and in some cases seems to be more problematic from mobiles or cordless/fixed phones that send a short duration DTMF burst.

Here is a link to the Linksys Admin Manual, it's big as it covers a number of units. It will explain (for the most part, and not always well) the settings as well as showing the defaults. http://www.ephonet.cz/files/1000066ATA_admin.pdf

The defaults are for the North American market, if you are in another area you will need to do a search on-line for specific settings for your country. These can make a difference with such things a level, quality of the line and echo.

 

[aznarepse]

Hi Leejor,
sorry, I probably didn't explain myself properly. I am in UK and indeed I have set up some regional settings to UK. Thank you very much for the link to the manual. I had more or less the same version and as you point out, it is not very generous on explaining settings.

So, you mention that the DTMF settings in the SPA will not affect an incoming call. Am I right in my assumption that the Mobile sends the DTMF as out-the-line, which will be converted to in-line tones by the analogue PSTN operator and they get to my SPA as in-line? (consequently passing through transparently to the 3cx?)

Many thanks,
Adan

 

[abc123]

Hi Adan

I looked at your wireshark capture and DTMF 7 and 8 are being sent. There is only 0.6 seconds between the end of the 7 and the start of the 8 so i am not sure if that is too fast for processing. You mentioned you had these in your phone memory. Can you space them out a bit more?

 

[aznarepse]

Hi Mark,
yes they are in the capture. However, the funny thing is that before those DTMF numbers, there were transmitted 1, 0 and 2 and the DR managed to get them. Also, after 7 and 8; other digits were also transmitted.

Is it possible that some digits are transmitted out-of-band and some in- band?

 

[abc123]

Sorry, I got caught up in some things yesterday afternoon.

I would think the 3102 FXO is not seeing all the DTMF tones and so passing them as RTP (which is why some are not showing but also still working at the DR).

I also did not see a single full DTMF event (usually it is 10 RTP Events for each digit followed by 3 RTP digit end events.

The other problem was all your RTP events had volume = 0. And their durations did not increase (should be 0, 80,160,240) and some even had the same duration.

Now you say that you have this programmed into your phone memory (I assume some form of speed dial). What happens if you did the call manually and pressed the digits from the same phone? Does it work then?

 

[SY]

I've seen this wireshark capture.
The problem is that SPA3102, in specified environment, doesn't provide unambiguous (reliable) delivery of DTMF signals received from PSTN line.
There are 8 DTMF signals received form PSTN.
First three bypassed as in-band(audio). Then '7' and '8' delivered as out-of-band (and cut from audio signal). Then last three digits delivered as in-band(audio) again. Why it happens I don't know but I suppose that the reason is very low volume of audio signal received from PSTN line.

Everything is working well until gateway starts to "jumble" between in-band and out-of-band delivery.

P.S. Mark, we've posted the same information synchronously

 

[abc123]

I am just glad to be on the same wavelength as you Stepan!

I have a hunch it is to do with the phone having the button pushes in the speed dial/memory. Even in the analog days if you didnt get your pauses correct then it didnt work.

I would like to see the same wireshark as before but with manual key presses.

But there are a number of factors that could be getting in the way of good tones reaching the 3102 including dirty/noisy telephone lines.

There again it could be the 3102 settings also but as you tried various ones with little success then it can get laborious.

I would just sit there with wireshark on and see if you can see any pattern as to what is and isnt getting through.

Or just dump the pstn line

 

[aznarepse]

Hi,
Stepan, Mark; thank you very much for your wisdom!
I see that it is as I was guessing; the SPA parses some DTMF but not others. I will try to increase the gain on the PSTN line of the SPA.
Mark, when I dial manually the DTMF the behaviour is similar. It works fine if I wait until the DR stops talking, but the SPA still passes through many DTMF. Which seems to confirm your hypothesis of low volume in the PSTN line.

I will let you know if I get some results by increasing gain.

Best,
Adan

 

[aznarepse]

Mark,
just posted and saw your new post.
I will email you a new wireshark with manual pushes on the keys. There is no difference.
Also, the dialling from memory works for other numbers I dial.
I believe it is, as you suggest, poor quality on the PSTN line.

Best,
Adan

 

[abc123]

Can you get a different gateway just to test?

 

[aznarepse]

Mark,
bad and good news!
Unfortunately, I don't have any other gateway to test...

The good news is that I have increased the value in "PSTN to SPA gain" field on the PSTN Line tab and it works!

Few things though:
I have had to increase it up to +6, which I believe is quite high and haven't tested yet what effects has over the rest of the communication.
I am going to try to change also impedance in the port, which might affect the quality...
Will also run a wireshark to see if the DTMF now are parsed or just pass through at a higher volume...

Best,
Adan

 

[abc123]

Great!

Let me know the results.