Showing results for 
Show  only  | Search instead for 
Did you mean: 
Aspiring Contributor
Message 1 of 2

VoIP DTMF signalling failing to pass-thru router



On Friday, 9th January 2015, I could dial into conference calls, enter my passcode and connect to the conference call. It did not matter whether I dialed the 0800 number or the 0844 number of the 020 numbers provided by the organiser of the call in each and every case it worked.


On Monday 12th, and today 13th (I left it a while to see if it would fix itself) I find that I cannot log into the conference calls with my passcode. The system acts as if I have typed in nothing. That is this is the case for all 08xx numbers. For some reaso the 020 numbers, for the moment, are allowing me to access using my passcodes.


I have rebooted the Router, I have rebooted the Polycom VVX400 VoIP phone but nothing has changed.


I have been in contact with my VoIP provider. They have looked at the logs and it would seem that as soon as the call is connected the line goes quiet, in the case of the 08xx and continues normally with the 020 numbers.


However, when I hang up they receive and IP END signifying the connection has ended.


Further investigation discovered the following:


  1. Product name:             BT Home Hub
  2. Serial number:              +068342+NQ34457438
  3. Firmware version:       Software version (Type A) Last updated 10/01/15
  4. Board version:              BT Hub 5A
  5. DSL uptime:   0 days, 05:34:59
  6. Data rate:       19999 / 72516
  7. Maximum data rate:  24463 / 72208
  8. Noise margin:               15.2 / 6.2
  9. Line attenuation:         17.7 / 15.4
  10. Signal attenuation:   17.7 / 15.4
  11. Data sent/received: 138.1 MB / 1.0 GB

That is the firmware was updated on 10th April, as in Saturday. 


Now everything worked on Friday, then the fault appeared on Monday. This would suggest that the firmware upgrade on the 10th is the cause of the fault.


I have no idea how DTMF packets are sent and what rules are applied to such packets to route them, however if they are heading to an 08xx number from a Polycom VVX 400 it would seem your new router software is blocking the transmission.


Please advise when this might be fixed. For the moment I have switched to the 020 numbers, however these are charged and as its a VoIP connection the payment is not going to BT. I guess your incentive to look at this is low, but my phone bill is likely to be the issue here ...


Thanks for your attention, I hope you have enough information to determine the issue and correct it in some way.

Best regards,



0 Ratings
Distinguished Sage
Distinguished Sage
Message 2 of 2

Re: VoIP DTMF signalling failing to pass-thru router

Welcome to this forum.
This is a customer to customer forum only,


This is where customers help each other get the most out of BT products & services.

Anything you post here does not go to BT. Although the forum is moderated by BT, not all posts are read.


If you need direct help from BT or have an urgent problem please use this linkContact Us.


This is a public forum which can be viewed worldwide, so please do not post any personal information, especially phone numbers, account numbers, fault numbers, address information or email addresses, as this could be used to impersonate you.

If you are a business user, please could you post on the BT Business forum at



0 Ratings