I have a remote location that is homed off of our Call Manager. The remote location is connected iva a point to point T1. I have had 2 cases open with Cisco Tac for echo issues. Each time afte making the directed changes on the gateway, the echo went away for a couple of days and then returned. Anyone have any Ideas? i am about ready to turn this over to the Carrier and have them check their line.
1. make sure echo cancellation is turned off on the T1 circuits. Talk to carrier.
2. check echo cancel coverage on your router. If it is default (16 ms) increase it to 32. this is done under the voice port for H323 calls.
3. make changes to your input gain and output attenuation on the voice port (for h323) or on the CCM GW config page (for MGCP). More positive input gain means higher volume into the voice port, and also more feedback. you might want to reduce it.
4. check if your carrier has set their impedence to 600 ohms. This is the default, but I have seen some carriers change it. If it is different, you have to change it too.
We have had pretty good luck with the newer g168 enhanced echo cancellation - if you have the capability to do it, you will see that your max echo cancellation coverege goes out to 64 - if you set it to 64, you invoke the new style, which besides having longer coverage, has faster convergence, and several other improvements. I did not believe the hype when it first came out, but the proof is in the pudding:
I have made those changes on the VG200 gateways that both locations share, and the echo went away for a couple of days and then returned. the only thing different is the router at the remote location. I have someone checking that now. Both locations calls go through the same gateways to get to the PSTN so you would think that both locations would have echo.
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