[cisco-voip] Static on 7960 Series Phone

[Robert Singleton]

On Tue, 2007-08-14 at 16:22 -0400, Cauthen, John A. wrote:
> We have an issue with one of our 7960 series phones continually to
> have static / crackling while the phone is in use.  It does not happen
> on every phone call but does happen usually every day.  We have
> contacted TAC support and have gone through the following
> troubleshooting but cannot pin point the issue.


> 1. Phone has been replaced twice

Same switch port

> 2. Taken a non reported static phone and placed in her office, static
> gets reported

Same switch port

> 3. Taken her phone out and had another user use it and no static
> reported

Different switch port

> 4. We have run a new cable from her phone to a port outside her office
> that has no static and she still get's static

Oops, different switch port, but has static.

> 5. Office has been checked for interfering devices (none found)

So, the office has nothing but furniture and the phone in it? How about
a PC monitor with connected to an outlet with a bad ground or otehr
wiring fault? How about the adjacent offices? Cabling that doesn't
necessarily terminate in that office but passes through the walls?

> 6. Static reported by her as being so bad she cannot hear the person
> she is talking to all the way down to just crackling (like cell phone
> reception), but the person on the other end does not hear static.

Have you tried the call statistics during the static time to see if
there is jitter or dropped packets? Sounds like something that is
specific to her calls; is the static only on outbound calls or both? If
only outbound, maybe her Device Pool has her in a region that can only
use a high bandwidth codec, but insufficient bandwidth is available?
Until the different switchport with the same issue came up above, I
thought that perhaps her switchport was limiting bandwidth or something
like that.

> 7. Have applied the latest and greatest phone load to user’s phone

Generally a good practice anyway...

Is the phone powered by the switch or a separate power supply? If a
power supply, maybe it has a noisy connection.

I'm tapped out for now...

Robert