Im troubleshooting an issue with echo. The problem is occurring only on PSTN calls. The issue seems to be random in that it does not happen on one particular phone all the time and it does not occur on every single call. We have CallManger 4.1(3) supporting 125ish phones, most of which are 7941 and 7961 models. We have a single PRI in a 2811 router using MGCP. (See below config). The users complaining about this issue say they are not using the speaker phone or a headset. I also verified that the volume is not cracked to the max setting on their phones. The echo seems to crop randomly on a call and can last upwards to 30 seconds. Any hints from the group would be appreciated. The gateway load is 12.4(7).
network-clock-participate wic 0
network-clock-select 1 T1 0/0/0
isdn switch-type primary-4ess
controller T1 0/0/0
pri-group timeslots 1-24 service mgcp
no ip address
isdn switch-type primary-dms100
isdn incoming-voice voice
isdn bind-l3 ccm-manager
no cdp enable
ccm-manager redundant-host 10.10.16.16
ccm-manager config server 10.10.16.16
mgcp call-agent 10.10.16.17 2427 service-type mgcp version 0.1
If you do a sh voice port on the T1, you will see your echo cancellation coverage - it should be at 64ms, that means you are using the newer E168 echo cancellation, which is much improved from the old stuff. If it is something else, then set it to this as a starting point, and see where you are. Then you best bet is to adjust your levels on the voice port - you want to get it so there are no volume complaints, but hopefully you crank down the signal that is being echoed back so you don't notice it. We usually start with +3 attenuation and -3 gain, and see how that goes. Here is a link to a short doc on troubleshooting echo:
I tried 12.4(2)T3 and 12.4(4)T2 and had some echo. I believe the DSPware was 6.3.4. TAC sent me the DSPware version 4.4.18 and 4.4.12, which did fix the echo issue, but it also presented a nasty issue of voice cutout on the IP phone side during the first 10 seconds of about 95% of the calls. I upgraded to 12.4(6)T2, removed the DSPware file they sent me from flash, so it used the built-in DSPware in 12.4(6)T2 which is 7.4.1. I made about 30 calls and didn't have any echo or voice cutout.
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