We have run into echo problems with CallMgr & 79×0’s numerous times. We have followed Cisco’s instructions to resolve, but customers continue to complain about echo. We can’t seem to nail down a pattern.
This problem may be associated to acoustic echo experienced by users, or it could be a gain issue.
Initially it would be recommended to reduce the volume on both phones, receiving and transmitting. Its possible that the volume is too high and that sounds coming out of the receiver (handset) are being transmitted to the user. So reduce the volume on both phones. Cisco Usually recommend 75%. I would say slightly less than that.
There is a facility to lower gain in your primary call manager/Publisher box. You can increase or reduce this accordingly you should notice significant changes. You can also change this setting within your SRST router if you have one.
If you require more details feel free to email me or reply post. Hope that helps!