[cisco-voip] Clicking/popping noise on inbound side of PRI

[Mike Armstrong]

Sorry, I neglected to cc the list when I replied to Scott yesterday; here's
the essence of it:

We use 1-20,24 because we're only paying for 20 channels.  I also questioned
this, but TAC didn't raise any
flags.  Also, everything worked fine for 8 months, so I'm fairly confident
this isn't it.

Late breaking news... Last night I spent about 1/2 hour of quality time with
the
people who built the SmartJack.  It has a control port on it -- an RS-232
connection for a VT-100 to do all sorts of diagnostic stuff.  I used it
yesterday
morning to do some loopback testing with no problems.  However, there were
no errors this morning either.  Tonight, I tried to do the same, with error
rates approaching 100,000 in a 15-minute interval, and the VT-100 stuff was
unusable.  The screens were unstable, the SmartJack acted like it was
seeing random input from my laptop, etc. -- a real GIGO situation, but I
wasn't inputting anything, let alone G.  The Adtran guy was baffled -- said
he couldn't account for that at all.  We disconnected the ground, the
router, and my laptop power supply, leaving the SmartJack connected only to
the Telco line and the laptop, which was now running on battery power
alone.  The problem persisted.  Mr Adtran was even more baffled -- said if
he was trying to design a SmartJack to do that, he wouldn't know where to
start.

The SmartJack derives its power from the HTU-C at the other end of the span.
Suspecting dirty power, we're eyeing the span power now, but don't know how
to measure/diagnose it.  As a
first cut, we decided to ask Verizon to plug in a passive T1 monitor on the
customer side of the SmartJack for a while to see if they see errors there.
They're supposed to show up Monday.
If they see errors, the theory goes, it's their problem.  I like your
approach, though.  Curiously,
Verizon showed up last week to install another T1, which terminates right
next to this one.  Problem is, nobody has any idea who ordered it, or what
it's for.  Maybe I'll make use of it.

Mike Armstrong
University of Florida CREC
Lake Alfred, FL
863.956.5891
----- Original Message ----- 
From: "Vance Shipley" <vances at motivity.ca>
To: "Mike Armstrong" <mfa at lal.ufl.edu>
Cc: <cisco-voip at puck.nether.net>
Sent: Friday, September 19, 2003 6:01 PM
Subject: Re: [cisco-voip] Clicking/popping noise on inbound side of PRI


> Mike,
>
> I would want to run a 24 BERT test from the CO to the Cisco.  Put the
> Cisco into remote loopback mode and have Verizon run a BERT test through
> that loopback.  This will test the Cisco LIU, the cable, the SmartJack
> and everything else out to the CO.  You need to do this for 24 hours
> 'cause you don't have a 100% failure rate.  If you could reproduce the
> eoors all the time you could draw conclusions earlier but as it is you'll
> need to run long enough to know that you would have seen the problem.
>
> If that test shows errors then you would want to restest with the loopback
> being provided by the SmartJack.  If it still shows errors Verizon will
> accept responsibility and fix it.  If not Cisco will blame your cable or
> take resonsibility.
>
> Now as far as the cable goes, what is a "certified cable"?  Is it a
> certified RJ-48C cable?  Or is it an ethernet cable?  I don't believe
> a lack of sheilding is going to cause this problem however you need
> to make sure you have your signals on twisted pairs.  RJ-48C uses pins
> 1&2 and pins 4&5.  You must have pins 1&2 use a twisted pair, and the
> same for pins 4&5.  A flat "silver satin" cable will not work.  A cable
> where the white-blue/blue-white, etc. pairs are not using the right pins
> will not work.  A combination of two wires where one is <color> with
> white stripes and the other is white with <color> stripes makes up a
> twisted pair (e.g. white-orange/orange-white).
>
> 99% of the time these sort of problems are caused by cabling/connector
> issues.
>
> Next question:  where are you deriving timing from?  You must be
> clocking off the incoming T1 from Verizon.  If you are using an internal
> clock, or clocking off another span which is not itself timed off
> Verizon (or a higher Stratum level) you will have problems.
>
> -Vance
>
>