FXO 2921 Static issue

[steigja]

Hello All,

    Ive been battling this issue for a while.  So we have a 2921 voice gateway router with 4 FXO port outbound to telco.  The issue is that outbound and inbound calls have static.  Its a background static you can hear in the back of the call.  The external party never hears the static, its always only heard from the internal phones to the PSTN.  When I connect my butt set to the voice gateway's FXS ports and dial out I hear no static.  When I connect my butt set to the rj11's that go to telco I get no static.  The version of code on the router is universalk9-mz.SPA.154-3.M1.bin.  

Things I have tried.

- Had Telco come out but they heard no static from there demarc outbound.  They also checked there pole and they where clean.  So Telco is out as the issue.

- Replaced Chassis and DSPs,  I had a TAC case opened and this equipment was replaced but it didnt solve the issue.

- We have 6900 and 7900 phones with 9.x call manger.  Internal calling is fine.  All phones have static outbound.  

- Ran THL sweep and it recommend complex5, i set that but it didnt fix the issue.

Anyone have any suggestions?  I'am concerned about a few things and one is grounding.  If the rack is not grounded it could cause these type of issues correct?  What about any other settings I can try on the FXO ports.  What about hardware line filters I can place on the cable to telco, i heard DSL line filters might be able to help with the issue.  Thanks everyone!

FXO port configs

voice-port 0/2/0
no comfort-noise
connection plar 590
impedance complex5
caller-id enable
!
voice-port 0/2/1
no comfort-noise
connection plar 590
impedance complex5
caller-id enable
!
voice-port 0/2/2
no comfort-noise
connection plar 590
impedance complex5
caller-id enable
!
voice-port 0/2/3
no comfort-noise
connection plar 590
impedance complex5
caller-id enable
 

[chrihussey]

Any particular reason for the impedance configuration on each port?

[steigja]

Chrihussey,

   I have removed the impedance commands as they werent helping,  i have also readded the comfort noise but the same issue occurs.  Thanks

Jason

[chrihussey]

Sorry I missed that you ran the sweep test.

Yes grounding the rack and/or the router could possibly help. You could also have the outlet checked that is powering the router, specifically the ground on that.

Also check to make sure there are no power lines, strips or fluorescent lights close to the cabling. Not just for the FXO lines, but for the Ethernet cables too.

Had a long standing intermittent issue at a site with static and noise and it turned out the PRI lines were run along side some power cables. Once re-routed it all cleared up.

[steigja]

Thanks chrihussey,

     I think i'am starting the narrow it down.  Its super odd because when i'am talking on an outbound call and i'am in another room and people are in an adjacent room.  I can hearing the cross talk from them having a conversation, like I cant hear words but I know there is talking.  The overhead speaker system is actually right behind the rack where the equipment is.  I'am thinking it might be causing the issue.

Jason

[chrihussey]

Wow, you might be on to something.

Best of luck.