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By d3tafaq
#1069
Hi all,

I have issue with the loop start signaling with BT. :shock:
If we have incoming call from analogue trunk with BT Caller ID, but we don't answer it. After some time the CO finishes the call, we detect the last RING and start wait 3 sec. for clear the call. BUT at this time point, we receive the next incoming call from CO with Caller ID. We can't detect Polarity Revesal until we finished the previous call. As result we don't detect Caller ID message for the second call. It's problem. :(
And question, which of docs or standards describes this problem and how we can solve this problem.
What means, if we receive the Polarity Reversal in the ALERTING state, Is it constantly means the new call and we can clear the previous? Or there may be other ways to solve this problem? :roll:

Thanks :)
P.s. Sorry for my English. :)
By GoofyCyborg
#1071
d3tafaq wrote:And question, which of docs or standards describes this problem and how we can solve this problem.
You may want to look at BT's documentation here: http://www.sinet.bt.com/sinet/SINs/

It may also be well worth your time asking over on the BT business forums: https://business.forums.bt.com/
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By WelshPaul
#1075
You got me scratching my head at this one!

I understand your issue, you explained it well but coming up with a fix is beyond me. I have very little experience with with CO/PBX also known as TDM-based PBX (Time Division Multiplexers) which is what I believe you have? What hardware are you using?

I might know somebody who may be able to help or point you in the right direction. That's a mighty big might mind! :)
By d3tafaq
#1097
We use PBX, with CO connection, via analogue trunk.
We got the problem after start to support the BT CLIP, early we don't detected, what two calls was stuck together.
And I want to know, how it handles on CO level and how it works on other systems.
In USA, for example, these problems do not detected, because CO can handle these vulnerabilities.

OK thanks, what VPN are you using ??

A good write up on SIP ALG: https://www.voicehost…

Thanks very much. Really appreciate it! :-D

Attached below is my latest OBIHAI UK configuratio…