Solved Snom D710 - DTMF key tones

[AWS2P]

Hi,
I'd like to know where to search and set DTMF key tones on D710, last week I wanted to select options on remote IVR but no DTMF was heard when pressing a key.
Is there only on phones settings or also on SIP trunk I need to search?

 

[JohnS_3CX]

Hi @aws2p

By default we configure phones to send DTMF in RFC2833.

If you call a remote IVR, there is always a small chance that even though you send the correct DTMF signal, the other side still fails to understand it.

Examples:
1. your phone, your pbx, and your trunk provider accept and correctly process RFC2833 (all good until here)

2. the other provider says they accept 2833 but they do not pass it on to their destination (DTMF breaks)

3. the other provider provider accepts 2833, and the destination PBX accepts it, but ignores it internally (DTMF breaks)

4. the other provider provider accepts 2833, but the destination PBX does not accept it. Their provider fails to fallback to in-band (DTMF breaks)

5. The other side does not accept 2833 at all, but their provider fails to inform your provider about it during the invite. (DTMF breaks)

6. The other side does not accept 2833 at all, so your PBX reacts correctly and sends in-band, but due to codec transcoding that takes place outside of your PBX, the in-band DTMF is too degraded, and the other side cannot hear it correctly (DTMF breaks)



So you see, there is no perfect solution here, ultimately it is always a best effort. Do you really need to go and change everything on your side, just because some destinations will not accept DTMF correctly? (and even if you do, you might break other destinations that used to work fine).

 

[AWS2P]

Hi @JohnS_3CX
to be more specific on extension 111 (D710) I can't use DTMF on any destination I call. Pbx and phones are local LAN.
beside I have a D785 ext. 102 connected to the same PBX and trunk and on same called numbers are working fine on IVR (DTMF tones are heard) and of course key pressed are producing a real effect

 

[JohnS_3CX]

Start by investigating the basics:

1. Factory reset the phone to make sure there are no old settings left inside
2. Ensure firmware is 8.9.3.96
3. Delete its MAC from the current extension and press OK
4. Assign the phone to a brand new extension
5. Once it is provisioned, call an internal IVR first and see if it works (if yes then you are OK)

Can you confirm its ok until this point? (we can continue from here later)

 

[AWS2P]

After doing all your steps phone is working with internal IVR and DTMF tones are heard when key pressed

 

[AWS2P]

now i can't reassign it to extension 111, phone appears in bold, when i choose assign to extension 111 nothing happens
Phone Ip was in blacklist, ok now phone returns to his previous extension and DTMF tones are always there , YYYYesss

 

[JohnS_3CX]

Ok sounds good! So if your internal IVRs work then the phone is fine.

You can also try external ones too, but remember, in case of failure you will need a capture from the PBX so we can see exactly what happens during the DTMF transmission.

 

[AWS2P]

Hi problem seem to be back again on Snom 710 i can't use anymore DTMF on this phone.
I needed once again to factory reset and re-assign existing extension, so now it works again but for how long ??

 

[JohnS_3CX]

Reboot the phone once, and tell me if the problem "magically" goes away.

 

[JohnS_3CX]

I seem to remember the bug with older Snom phones where DTMF would stop working after some time.
Rebooting makes the problem go away until next time. There are some older threads on this exact issue and Snom had fixed this since at least version 8.9.3.80:

• SAP-609 FIX: Snom 710 / D710: Loss of DTMF or Call Waiting tone after ~280 calls received
• SAP-1573 FIX: Snom 710 / D710: DTMF (in-band) stopped working after ~400 calls and needs a reboot to recover it

Perhaps the issue was not entirely fixed maybe? Since this is an older model, I don't think it will be receiving any newer updates so you may be stuck with this problem forever..

 

[AWS2P]

Reboot the phone once, and tell me if the problem "magically" goes away.

before factory resetting the phone I just tried to provision with no change, next time i will try a phone reboot.
My Fw is up to .80 as last release is 8.9.3.96
I tried to open a support on Snom side even phone seems already out of their scope.

so you may be stuck with this problem forever..

humm... not forever, but almost until I change the phone by a new one not affected by this silly problem looking more as planned obsolescence. It seems so stupid with phones in good condition to be obliged to threw them away only because their commercial support time is ended.

 

[AWS2P]

Hi,
Well, I paste here the Snom support answer confirming an existing bug but without fix .

Snom support answer

Hi,

I've looked into this internally, and unfortunately I can confirm this was a bug randomly affecting some desk phones, and it was solved definitively on firmware 10.1.39.11: being the Snom 710 an End Of Life product the version you are using 8.9.3.96 is the latest one we released, and the fix isn't available for that specific product I am afraid.

The only work around we can suggest to try is to set the parameter below

https://service.snom.com/display/wiki/user_dtmf_info

To "on", so that the phone will use both SIP info and RFC 2833 DTMF, with the first ones generally not affected by this issue as much as the default ones.

Thank you

Is the setting Snom ask to change overwritten by automatic provisioning each 24h ?

 

[JohnS_3CX]

We do not overwrite that value, you can try it if you want and see, but we support RFC2833. SIP Info might not work well.

You could also inform the user that whenever the problem occurs they can restart the phone and it should be ok for a while.

 

[AWS2P]

Ok, thanks John for the tip, just hard to accept this as it is a known bug by Snom and nothing is done even if it's EOL, surely if it was the same problem on all Snom's fix could be the same, so probably not a hard work to fix it, finally my options are to reset the phone each time DTMF decide to vanish or change by a new model not affected, what a deal !!

I hate planned or forced obsolescence

 

[JohnS_3CX]

Yes, I guess the solution is just a reboot every now and then to avoid the issue.

Sorry I couldn't be of any further assistance on this.