asterisk users - Oct 2006 - Echo problems on ISDN. (mainly incoming calls)

OK I have been battling with echo problems with asterisk on ISDN for a 
few weeks now, and still can't solve it (although I think I have tried 
everything I can find.)

I will try a post everything I think is possibly relevant that I can 
remember with the hope someone can point me in the right direction.

current spec I am using (Trixbox 1.0 was still in beta at the time an 
didn't detect the TE110 card, and modules didn't load properly when I 
tried manually either )

Asterisk@home 2.8
Wildcard TE110P ISDN PRI card (set to E1, I live in the UK)
Telewest Q931 ISDN connection (currently 8 lines 100 phone numbers)
dell SC1425 server (3.2 Ghz, 512MB, 80GB)
SIP phones aastra 9133i run 1.4.0 firmware.

This is on a live system with about 50 users. (I have a identical system 
for DR so can easily test out of hours)

Most the time there is no echo,
If I phone my wife (on a normal telewest analog line) I get a slight 
echo (fairly quiet) that she does not noticed. This happens on other 
phone calls but the user can tolerate this (would prefer to solve it)

If a big customer (one with several thousand employees) phones me, I can 
hear a very loud echo with an annoying delay (0.5-1.0 sec, ish), which 
the users cannot tolerate. The customer does not get the echo, currently 
the user phones back?

Any suggestion on How to solve the echo problems?

I have tried with echo cancellation at 800 and changing the RX and TX 
gains to no effect. I have read that ISDN should not have echo problems 
and that may I sould ask about the gains on the line provided by the 
telco. Can anyone give me more information about this as if I phone 
Telewest I want to pretend that my PBX supplier has told me to ask XXX. 
As the first thing they ask me is to contact my my PBX supplier (I had a 
slight problem getting the ISDN card to initially connect)


Thanks

John

Please read these with care:

Causes of Echo http://www.voip-info.org/wiki/view/Causes+of+Echo

Asterisk Echo Avoidance: http://www.voip-info.org/wiki-Asterisk+Echo+Avoidance

Until you understand echo it will be impossible to eliminated it.
Notice that you have a digital connection and your SIP phones are the
same. The echo is caused at the other end of the call. Have you any
VoIP providers to test with? You will probably have the same results

--Andrew



On 10/11/06, John McEntee <john@mcentee87.freeserve.co.uk>
wrote:
> OK I have been battling with echo problems with asterisk on ISDN for a
> few weeks now, and still can't solve it (although I think I have tried
> everything I can find.)
>
> I will try a post everything I think is possibly relevant that I can
> remember with the hope someone can point me in the right direction.
>
> current spec I am using (Trixbox 1.0 was still in beta at the time an
> didn't detect the TE110 card, and modules didn't load properly when
I
> tried manually either )
>
> Asterisk@home 2.8
> Wildcard TE110P ISDN PRI card (set to E1, I live in the UK)
> Telewest Q931 ISDN connection (currently 8 lines 100 phone numbers)
> dell SC1425 server (3.2 Ghz, 512MB, 80GB)
> SIP phones aastra 9133i run 1.4.0 firmware.
>
> This is on a live system with about 50 users. (I have a identical system
> for DR so can easily test out of hours)
>
> Most the time there is no echo,
> If I phone my wife (on a normal telewest analog line) I get a slight
> echo (fairly quiet) that she does not noticed. This happens on other
> phone calls but the user can tolerate this (would prefer to solve it)
>
> If a big customer (one with several thousand employees) phones me, I can
> hear a very loud echo with an annoying delay (0.5-1.0 sec, ish), which
> the users cannot tolerate. The customer does not get the echo, currently
> the user phones back?
>
> Any suggestion on How to solve the echo problems?
>
> I have tried with echo cancellation at 800 and changing the RX and TX
> gains to no effect. I have read that ISDN should not have echo problems
> and that may I sould ask about the gains on the line provided by the
> telco. Can anyone give me more information about this as if I phone
> Telewest I want to pretend that my PBX supplier has told me to ask XXX.
> As the first thing they ask me is to contact my my PBX supplier (I had a
> slight problem getting the ISDN card to initially connect)
>
>
> Thanks
>
> John
>
>
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