asterisk users - Sep 2005 - Cisco 7960 Locking Up

Ok...  I asked a question a few months back about a 7960 that a user 
claims to be "shocking" her in her ear from time to time.  A few
others
indicated they had similiar issues and alot of them seemed to stem from 
power over ethernet.  Here's what we've done...  We replaced the phone, 
ran two new cat5 cables to a different switch, put in a power brick and 
disabled power over ethernet.

Over the last few months, the number of incidents of her getting shocked 
have reduced to almost never, but the phone is displaying the same 
symtoms as when she was getting the shock.  The phone seems to lock up.  
We can not establish any type of pattern as to what causes it, but 
here's what we do know.  She can be on a call and not touch any 
buttons.  The soft keys will blank out and she loses audio as does the 
person on the other end.   This has happened over both Zap and Sip 
channels.  The strange thing is that if she waits about 20 seconds, the 
LCD panel will sort of flash and she gets the call back!!  I never see 
anything in the CLI that makes me think Asterisk is even aware it is 
happening.

I've done some research and I found some people have had issues with 
cell phone radiation locking up or rebooting a 7960.  Has anyone else 
experienced this?  We tried removing her cell phone from the room and it 
doesn't seem to make any difference.  We do, however, have a cell phone 
repeater set up, but it's closer to alot of other users than her.  
Anyone have any suggestions on how to debug this?  Is there some type of 
logging meter we can buy or rent that we could stick over there and 
monitor the environment for a week or so?

As always, thanks for the help!!

Mark

I do recall your postings relative to this...
 
> I've done some research and I found some people have had issues with 
> cell phone radiation locking up or rebooting a 7960.  Has anyone else 
> experienced this?  We tried removing her cell phone from the room and it 
> doesn't seem to make any difference.  We do, however, have a cell phone
> repeater set up, but it's closer to alot of other users than her.  
> Anyone have any suggestions on how to debug this?  Is there some type of 
> logging meter we can buy or rent that we could stick over there and 
> monitor the environment for a week or so?
US cell phones generate such low RF power there is no way for any such 
equipment to impact a 7960 (and you've already proven that). The same
is true with cell repeaters and/or towers. (US cell equipment is rated
in terms of milliwatts of power.)

The issue is most likely static electricity generated by something. 
Probably should focus on ruling that out as a possibility. If it is 
a static charge, it could originate from her clothing and sliding
around in her chair, shuffling her feet on the carpet, etc. Using
a static mat under her chair might help and/or some of the anti-static
sprays that are available.

I'd be inclined to put an AC voltmeter between a metallic part of the
7960 and a true ground point. (Getting at a metallic part of the phone
might be a trick since the phone is probably UL listed and doesnt' have
any exposed metallic parts. And, finding a true ground point in the
office might not be easy either. In the US, the round ground prong on an
AC outlet "should be" a true ground depending on how will the
electrian did his work.)

I'd also check the grounding of the rack that holds the PoE switches
just to ensure the source isn't coming from that area. Since you've
found "...reduced to almost never..." with the changes that you've
made,
I'd have to suspect a real grounding problem back in your switch racks,
etc.

FWIW, the folks that engineer central office telephony equipment (including
racks, etc) are fanatics about rack grounding for some very good reasons.
Some electrians understand that very well also. Most of those issues
can be diagnosed with a standard high impedance AC voltmeter available
from Radio Shack.

In case you're not a believer (or don't understand rack grounding),
consider the case where a complete equipment rack is not grounded in
any form, and one piece of equipment in the rack develops a problem
where one side of the 110 volt AC commercial power is shorted to the
chassis. The equipment can and will operate properly, but touching the
rack and a water pipe tends to be an issue. ;) Since the equipment in
such a rack is generally connected (one way or another) to other racks
in the same room or building, one rack problem can certainly impact
another distant rack. Been there, done that, felt it, and had to fix it
for real.

You shouldn't need any specialized test equipment to diagnose either
a static electricity or grounding problem.