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Echo on small business phones when calling external

Unanswered Question

Hi All,

My customer has recently started hearing echo intermittenly when calling the PSTN and also when the PSTN calls them. Note the PSTN end no echo is experienced.

There are 8 analog trunks and all of them i have enabled echo cancel coverage 48ms. So far we are monitoring however can someone advise how i can go about troubleshooting this issue. This issue recently occured after a power outage, i am not certain if this had anything to do with issue but i am letting you all know. Additionally the Telco has ruled out that the problem is not them.

Please assist.

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jeliasoncisco Tue, 04/16/2013 - 17:29
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Hello There. I assume this system is a UC500 system. Have you tried modifying the Codec settings on each PSTN Trunk? You may need to follow the instructions here to find the exact match for impedance on the copper loop from the telco. Once matched, your echo cancellation will work appropriately. This is a key need for any Analog PSTN Trunk connection to IP Phone System.

You may be able to use the automatic test, however, in my experience you have to test each codec individually then apply the one with the highest value.


David Trad Tue, 04/16/2013 - 18:51
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Hi There,

I do not believe this to be a Carrier issue but more so the UC-500 and the type of phones, I have seen this many times on the SPA-500 series phone connected to a UC-500 and then using PSTN lines, but the problem is actually decreased a considerable amount when we change them to the 7900 series phones, in most cases with it disappearing.

You can lower the gain levels (*CLI ONLY) but what happens is that the audio loudness can at times get too low.

On trick to try is to lower the volume level on the handset down by 2 notches, this seems to reduce it for some reason, but it wont work if you are doing speaker phone.

The only other solution is to try and convince your client to go to BRI and get a couple of ISDN lines, I have never seen this problem when running digital lines, only analogue.

Just a though


David Trad.

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jeliasoncisco Wed, 05/01/2013 - 18:10
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Hi there,

Just wondering if you were able to find a solution to this problem?

Thanks for letting us know.

paolo bevilacqua Thu, 05/02/2013 - 05:47
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You have two excellent answer above, other than that there is no solution.

Alexander Maroukian Thu, 05/02/2013 - 13:47
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The issue could be caused by different reasons.

I would suggest opening a case for this and you will find the root cause and solution.

Also sometime this is caused by headset(usually not set properly or not compatible) if such has been used.

Best regards,



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