DTMF not working from 5340 handsets

[BLucky]

We are having an issue on several 5340IP handsets trying to dial DTMF tones during a call.
When a user dials out to our BTMeetme conferencing service (connected via a C&W ISDN30) and is prompted to enter their user ID the digits are not recognised. The problem is intermittent and seems to be affecting several handsets. The users have resorted to transferring the call to the secretary who enters the digits for them before transferring the call back to the user. Swapping out the handset seems to help, but hasn't totally eliminated the problem.

Has anyone else had any similar issues?
Where are DTMF tones generated, at the handset itself?
Is there any way to boost the amplitude of the DTMF signal?

Any help would be much appreciated

[bobcheese]

DTMF is generated during the E2T function of either RTC or E2T card (depending on the size of your system). Is there any differences between the 5340's and the reception phone? By this I mean different VLAN, Teleworker set etc.

[BLucky]

Hi Bob,

Thanks for the quick reply. We only have a small system of approx 50 handsets all on the same VLAN.
All of the handsets including the secretaries are 5340's.

I'm glad you have clarified where the DTMF tones are generated, I had assumed the same but read elsewhere that it was on the handset itself.

Not sure where to go next. Are there any tests or traces I could perform to help locate the problem?

 

[bobcheese]

Just to clarify, as I understand it, the tone is generated at the set but as this is an IP set the signal is within the IP packet. The system then translate via e2t to TDM DTMF for transmission on the ISDN. does the fault occur on all phones? Any using compression?

[ralph]

What type of trunks are you using?   PRI or Copper CO?

Ralph

[bobcheese]

OP states C&W ISDN30 which is E1 PRI (cable & wireless)

[BLucky]

Hi guys, sorry for the late reply, have been away for a few days.
Fault is very intermittent and has occurred on several handsets. These handsets tend to be in the meeting rooms as this is where most conference calls are made. Personally I have not been able to replicate the fault. I was told today the guys had the same issue connecting into our internal conference server (an asterisk box connected via SIP trunks).

I have activated call statistics on the Mitel to capture the call information but when I look at the call that failed I cant see anything that stands out as unusual.

Codec used in all calls is G.711 (A-Law)

Does the fact that the problem has occurred on both SIP and ISDN trunks mean the problem is more likely to be with the handsets than the E2T end of things?

[ralph]

The E2T wouldn't come into play until the call touches a TDM device/trunk.   
So I would think the E2T wouldn't be the issue here.
But at the same time, I'd be hard pressed to think it's the 53xx set.

Is there anything else common between the external Conf bridge and the astrisk call bridge besides the 53xx sets?

Ralph

[Chakara]

  I'm curious - on PRI isn't the DTMF really sent down the D channel as commands rather than audio?  If so would a q.931 trace reveal anything? 

  I had a similar problem on a Cisco phone system, but the difference was the set having the issue was analog so the problem was in the analog ports DTMF detection.

-Chak

[BLucky]

Looks like we may have found the problem. It seems that all the conference calls are being set up using the phones loudspeaker. It would appear that the microphone on the 5340IP handsets are susceptible to picking up DTMF tones from the loudspeaker and resending them. The higher the speaker volume the more the problem occurs. Any volume setting above 8 (max 12) seems to cause the problem. A string '1234567890' sent at volume 12 actually sends '1223445567788900' for example. The problem took a while to find as whenever we tested we would either lift the handset or turn the speaker volume below 8 to avoid annoying everyone in the office with blaring DTMF tones.

[BLucky]

For future reference is there a trace command that can be used to capture the DTMF digits? Can the EDT Trace command do this and if so what would be the correct format of the command? We ended up using the log file on our Asterisk box to show the problem but would have been nice to have been able to capture in on the Mitel 3300.

[ralph]

Actually I just seen this fairly recently.   It wasn't on a 53xx phone but a polycom conference phone.
The way I found it was to have the user call me from the phone and then hit some digits so I could hear it.
I heard the DTMF then an echo of the DTMF.
Having them mute the phone as they dialed in resolved it.

I'm unaware of any traces that can be put on to trace the call.

Ralph