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New Member

initial echo in IP phone calls

Hi,

We have an installation here of around 60 IP phones and we are connected to the PSTN using a VG200 with a PRI in h.323 mode. The users recieve an echo in the first 5-10 seconds of all their calls out through the gateway. Is this an experience that is normal and should be expected? If not, any suggestions on how I get rid of the initial echo?

Thanks in advance

Nikhil

7 REPLIES

Re: initial echo in IP phone calls

what version of call manager are you running?there is a bug in 3.1.2(c) that has an echo problems try upgrading

hope this helps

New Member

Re: initial echo in IP phone calls

I'm running 3.1(3a) on both the publisher and subscriber.

Thanks

Nikhil

New Member

Re: initial echo in IP phone calls

Change the vg200 from 323 to MGCP.

If problem persists adjust the attenuation and gain on the PRI

New Member

Re: initial echo in IP phone calls

We can use only 323 on the PRI that is coming in from the telco. It would be a big change to put through since the system is functioning fine with failover and all. I'm refraining from changing the attenuation and gain since it affects the entire system and might make matters worse, but if that's the way to go I can make the changes. A quick question, why is it that I recieve the echo in the initial 10 secs of the call only?

New Member

Re: initial echo in IP phone calls

If you are using echo cancellation on the voice-port, that is probably the cause. I don't think I've ever seen it last more than 2-3 seconds though. I believe this is caused by the initial buffer being filled. You may try turning echo cancellation off for a few calls and see if that is the cause. You may not need echo-cancellation enabled, but I would bet you do.

-Brian

New Member

Re: initial echo in IP phone calls

This is a known issue. Cisco is working on a solution but I am not sure when it will be announced or available.

However, you shold only experience the echo for the first 3 seconds or so, not 5-10. There are a bunch of steps that you can use to reduce this, check Cisco's site. I also have some good docs, send me an e-mail and I will forward.

You aren't getting IP phone to IP Phone echo are you?

Have you enabled echo-cancel coverage? Another method I have used is to set the output attenuation to an extreme negative value, this will make the voice on the remote end very soft. Start adjusting back toward 0db until the volume is acceptable. This helps but usually cannot get rid of echo completely. The gateway has to detect echo before it can cancel it so there is usually a few second before echo stops.

Hope this helps. Like I said this is a big issue and it is being worked on.

-Mark

New Member

Re: initial echo in IP phone calls

in some old cisco docs, when we fought echo for months, i tried the cablelength short cmd. we run echo cancel coverage at 32. there is a good doc out there

http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/voipsol/ea_isd.htm#xtocid543431

controller T1 1/1

framing esf

linecode b8zs

cablelength short 133

pri-group timeslots 1-24

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