Q.931 Error (Tandberg MCU)

[Airwave1]

Hi everyone!

Got an issue with my bridge (Tandberg MCU).

The unit supports 16 Video calls and 16 Audio (Telephone) call's and is set-up correctly to support this, I have had this working previously (5 months ago) but we rarely use this facility so I have no idea at all when we lost this service.

To explain what happens:

When no one is connected to the bridge it will allow one incoming telephone call only (no problem with video) but when any other telephone call is made to it gets the out of service tone we get this Q.931 error. I can however connect the same telephone call's if the bridge makes the call to the phone/equipment, in other words dialling out is not a problem, only incoming!

I will repeat what I said before, video conferencing is not a problem, only audio/telephone calls.

[jakob]

Did you get in contact with Tandberg's support team?
I think they sell their MCUs only with a support contract and usually they are quite helpful.

[vtjoe]

Hello Airwave1,

We also use the Tandberg MCU 16+16.


You probably already checked this but ---
make sure that the conference is set to more than one audio system. If you are using TMS to start the call and you tell it you are doing audio telephone calls, it changes this setting automatically for each individaul conference.

Now, what I think the problem might be....
check the provisioning on your PRI ISDN line - and/or the configuration of the local PBX.

It sounds like the PRI will only accept incoming voice on one channel. If that channel is busy, nothing else will connect.

You can test this theory by placing an inbound call. The Tandberg MCU will show you the line and channel. Disconnect the call. Place/recieve a video call. Check the MCU to see if it is using the same channel as previously used by the voice call. Then try to do a voice call into the MCU.

You can also try recieving one audio call. Then place a video call and a few other audio calls out. Then disconnect the first audio call. The channel that is accepting audio should now be free. Try placing a call into the MCU (while the outbound video and audio calls are still connected). If you connect, I would say that it is the PRI.

[Airwave1]

I have sent off special ISDN traces to Tandberg who after studying them have provided me an updated software version.
I installed this and it corrected the problem and I was able to make the maximum number of incoming telephone calls that the MCU would allow/was set for. However after installing this new software release the MCU was only able to make out-going call's to other video conference devices at ISDN1 (64Kbps), it could still receive incoming video conference calls at the full bandwidth.

I have sent this back to Tandberg and will await a reply, in the meantime I have re-installed the old software.

Thanks

Gareth

[Airwave1]

I have had feedback from Tandberg and they have told me that this problem is with my phone system and not with the MCU.
Hopefully me posting this has not upset them too much as that was not my intention!

Gareth

[jeff000]

I have had feedback from Tandberg and they have told me that this problem is with my phone system and not with the MCU.
Hopefully me posting this has not upset them too much as that was not my intention!

Gareth
If you have any other divice to connect your pri to I would try it and see if the same things happen. What is the Q931 message? If this is a standard PBX, the Tandberg should work. It sounds like they are saying, their MCU only works with certian PBX's.

[trapehzoid]

If you have any other divice to connect your pri to I would try it and see if the same things happen. What is the Q931 message? If this is a standard PBX, the Tandberg should work. It sounds like they are saying, their MCU only works with certian PBX's.

no, its not certain PBXs.. its people that don't know how to configure PBXs that are the issue. Its rare to have actual hardware incompatibility (especially with main stream stuff.. and PRIs). The problem is 99% of people don't really know how to configure their PBXs at this level of complexity. Most people simply outsource their PBX management, and even they screw it up.

I think the worst part of the H.320 world was people trying to make video work off BRI enabled PBXs.. people just could not configure their PBXs right.

[Sean Lessman]

no, its not certain PBXs.. its people that don't know how to configure PBXs that are the issue. Its rare to have actual hardware incompatibility (especially with main stream stuff.. and PRIs). The problem is 99% of people don't really know how to configure their PBXs at this level of complexity. Most people simply outsource their PBX management, and even they screw it up.

I think the worst part of the H.320 world was people trying to make video work off BRI enabled PBXs.. people just could not configure their PBXs right.

I second this statement, you hit the nail on the head.