[cisco-voip] CF off net low audio issue

[Countryman, Edward]

I was able to crank the input gain and bottom out the output attenuation.  Also required cranking the EC but was able to improve this significantly.  

There is now noticeable popping and hissing on the line but at least the caller can hear the audio.  I am going to also open an att (my carrier) trouble ticket.  Thank you! 

-----Original Message-----
From: matthn at gmail.com [mailto:matthn at gmail.com] On Behalf Of Nick Matthews
Sent: Thursday, August 27, 2009 6:17 PM
To: Dennis Heim
Cc: Countryman, Edward; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] CF off net low audio issue

We see a lot of these cases.

This is generally the cause / scenario:

The PSTN runs a long loop to a site.  At this site, the FXO has low
volume.  IP phone users don't notice it, because they turn the volume
up high on the IP phones to compensate.  Then, only call flows that do
not go through the IP phones have the problem.  What will happen then
is calls to voicemail, which do not have the IP phone gain configured,
will be low volume (especially if played back in email and do not go
back through the phone).  Plus, any calls that come in the system and
go back out, will have the volume lowered.

What is actually happening is the IP phone users are able to
workaround the low volume issue themselves.  The real problem is the
long loop to the router.  If you were to place an analog phone on the
line instead of the router, you would have the same problem.

The solution is to put input gain on the ports.

voice-port 0/0/0
input gain 6

This can be done in the middle of a call (live change) to troubleshoot.

The danger is if there is a low signal-to-noise ratio  If this is too
low, turning up the volume on the line will also make the noise on the
line very low.  The router has no way to enhance the SNR.  If this is
the case, your best bet is to find a gain value that makes things as
good as possible, finding a provider with a closer CO, or having the
provider try re-running your loop (good luck).


-nick

On Thu, Aug 27, 2009 at 11:47 AM, Dennis Heim<Dennis.Heim at cdw.com> wrote:
> I ended up opening a tac case. Tac has some special tools just for low level
> analog trouble shooting.
>
>
>
> Dennis Heim
> Network Voice Engineer
> CDW  Advanced Technology Services
> 11711 N. Meridian Street, Suite 225
> Carmel, IN  46032
>
> 317.569.4255 Office
> 317.569.4201 Fax
> 317.694.6070 Cell
>
> dennis.heim at cdw.com
> www.berbee.com
>
>
>
> From: Countryman, Edward [mailto:Edward.Countryman at provena.org]
> Sent: Thursday, August 27, 2009 11:46 AM
> To: Dennis Heim; cisco-voip at puck.nether.net
> Subject: RE: CF off net low audio issue
>
>
>
> Do you if there is a Cisco job aid for this type of work;  is most of this
> done in the router?  I don't necessary see anything on the CCM (mgcp) for
> this.
>
>
>
> From: Dennis Heim [mailto:Dennis.Heim at cdw.com]
> Sent: Thursday, August 27, 2009 10:37 AM
> To: Countryman, Edward; cisco-voip at puck.nether.net
> Subject: RE: CF off net low audio issue
>
>
>
> You will need to play with your input gain and output attenuation.
> Additional, you may also need to do a tone sweep in order to get things like
> impedance correctly tuned. Prepare to spend a lot of time to get those
> analog lines tuned correctly.... Been there done that..
>
>
>
> Dennis Heim
> Network Voice Engineer
> CDW  Advanced Technology Services
> 11711 N. Meridian Street, Suite 225
> Carmel, IN  46032
>
> 317.569.4255 Office
> 317.569.4201 Fax
> 317.694.6070 Cell
>
> dennis.heim at cdw.com
> www.berbee.com
>
>
>
> From: cisco-voip-bounces at puck.nether.net
> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Countryman, Edward
> Sent: Thursday, August 27, 2009 9:50 AM
> To: cisco-voip at puck.nether.net
> Subject: [cisco-voip] CF off net low audio issue
>
>
>
> I have several smaller physician offices that will forward their main # to
> an offsite answering service for after hours coverage.  The sites are all
> trunked with POTS lines connected to FXO ports on 28xx series ISRs.  So the
> incoming call on FXO port 1 effectively is sent back out on FXO port 2 etc.
>
>
>
> The problem I have is that the audio level the caller hears is greatly
> attenuated; almost beyond discernment.  However if I call the far end
> directly the call is very clear so it appears my router is the problem.
>
>
>
> Anyone have any thoughts on this?
>
>
>
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