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I
had
a situation once were a customer was complaining of regular corruption of a
database on a Unix server.
After
a couple of weeks of investigation and much head scratching I narrowed the
problem down to one of about sixty Specialix connected dumb terminals on
the
site.
The
corruption only seemed to happen when someone was accessing the database
from
that terminal so it was swapped out - to no avail.
Everything had now been ruled out, server hardware, operating
system,
database software, network components, PC's, dumb terminals & dumb
users - had to be the cabling...
Traced
the cable back from the suspect terminal and found a bare Cat5 UTP cable
was
resting across the top of a very large automatic roller door and running
within
inches of the large electric motor that operated it. Stood and
watched for
a while and when a forklift came along and activated the door corruption
occurred on the database. :o)
Brought their IT manager over pointed at it smiled and walked away
(a
third party had the cabling contract!).
After
nearly three weeks of high tech investigation it turned out a fork lift was
the
problem!
Anyhow, the
time
I spent on site generated some much need income for the company I worked
for at the time (ICL)!
If you
are running anywhere near an EM noisy environment and need to be certain
of signal integrity then use STP and stick it in a shielded
conduit.
(Shouldn't be necessary in a home installation though - suck it and
see!).
Anto.
Well - there are a few applications which use the 8 cores separately
rather than as 4 balanced pairs. STP might come in useful there.
Also, it's useful in factory / industrial environments. If you want
cable
to go anywhere near a blast-furnace, say.
I've never seen an application that called for it in a
domestic
/ office environment.
M.
-----Original Message-----
From: BUTLER, Tony,
FM [mailto:tony.butler@xxxxxxx]
Sent: Fri 31/05/2002 12:58
To: 'ukha_d@xxxxxxx'
Cc:
Subject:
RE: [ukha_d] RE: cat5 cable picking up radio ?
Mark,
If
CAT5 is designed for balanced signals, which are (relatively) immune to
interference, what then is the point of screened CAT5?
It's a question I've been meaning to ask for a while (following a
previous discussion about ethernet being balanced) and you've just reminded
me of it.
Any ideas?
Tony
You CAN, if you really feel like it, wrap the CAT5 cable in kitchen
foil, and ground one end, which will help a bit...
... But it's fundamentally a crap way to do it. If you're going to
carry signals over CAT5, then they need to be balanced. The whole point of
balancing is in the rejection of interference (such as shortwave
radio.)
Doesn't matter whether you're talking 10baseT ethernet, 100baseT
ethernet, or KAT5 audio... balancing is the only way to go.
M.
-----Original Message-----
From: Amar Nagi
[mailto:amar@xxxxxxx]
Sent: Fri 31/05/2002 12:37
To: ukha_d@xxxxxxx
Cc:
Subject:
cat5 cable picking up radio ?
I lay as a temporary solution a cat5 cable and i run audio
down
it to the a set of mulitmedia pc speakers in the bedroom.
and for some reason it picks up radio. I can hear
a radio program in the audio.
any ideas ?
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