Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Low volume on analog lines (FXO) on 1760


I have a site with a 1760 router with a VIC2-4FXO and 12.3(14)T3 IOS version. They have low volume on calls and can barely hear the person, same for calls that go to Voicemail also. The gateway is H.323.

We have adjusted input gain to the max, tried various input gain settings also and shut/no shutdown the ports to no effect. We have also tried every impedance setting with no change. I have tried doing the THL tone sweep command on the gateway and that never completes all the way, saids ERL to low. I suspect there is a line issue but the telephone carrier has been out a few times and never finds a problem with the lines.

Any ideas? Should we replace the 4 port FXO card?

Community Member

Re: Low volume on analog lines (FXO) on 1760

We have experienced the exact same issue here (only we are running a 2811 with 12.4(9)T3. The only fix is to replace the FXO card (We have a TAC open on this, but so far this has been their only solution). We have re-set the router, tried the shut/no shut, and even upgraded the IOS. I am still working to see if we can find out why this is happening.

Re: Low volume on analog lines (FXO) on 1760

Well, I had someone at the site today and we tried a home analog phone on the lines and calls there were also soft and low volume. So it is defiantly something external to the router but the carrier saids there stuff is fine and has been out once already. The supervisory disconnect also is a problem on these lines since when an external party hangs up the router port stays connected for awhile.

I also took opportunity to update IOS since I had someone out there to 12.4(16) but did not expect a change since the calls had issue seperate from the router.

Hall of Fame Super Gold

Re: Low volume on analog lines (FXO) on 1760

Where are you located? If In N.A. you should be able to order or consult with:

they specialize in hard to find equipment for conditioning difficult lines.

You should be able to fix the disconnect problem with a tone detect configuration if telecom can't delivery power denial.

Community Member

Re: Low volume on analog lines (FXO) on 1760


You fix this issue with two commands on the voice-port interfaces. One of them is "input gain", the other is "output attenuation". If you look at the FXO settings for this interface in CM under gateways, you will find them there. I would intiate a call and modify those parameters during the call, you will hear the difference and can decide on which levels are right for you.

Note; make these settings in CM if you are using MGCP. If you don't, the MGCP settings will overide the ones you made in IOS.


CreatePlease to create content