'Network cat5 cabling question'
part 0 417 bytes
If you get this mail, our network is working! (100M)
From: john pearson [SMTP:CWIA.COM] xero
Sent: Monday, May 11, 1998 6:26 PM
Subject: OT: Network cat5 cabling question
Thank you for reading
Is it ok to run 15 to 20 cat5 network cables through about 6' of metal
conduit (1-1/4" emt). I hope this is enough info.
Chris Eddy wrote:
> Yes, you are safe. Cat 5 and other twisted types (twisted pair, not
> mentally) are reasonably good at keeping signals to themselves. Think
> of phone lines on the pole.
I'd take this all with a "grain of salt". Six feet, you should get
away with it. Some longer distance, maybe fifty feet, you may well
I'm not actually sure what is meant by "cat 5". If it refers to
shielded lines, no complaints at all. If it refers to 10BaseT cabling
using 4 out of an 8-wire cable, then there is a trick as this is *not*
in fact twisted pair.
Telephone lines on the pole *are* twisted pair as they are carefully
balanced by regular swapping of individual pairs in a pattern (Gray code
variant - it's abit of a subject in itself); it it to *this* that the
"twist" refers. Pairs in a composite cable are actually twisted at
It's all about balancing out "crosstalk". The flat "strap" cable used
with "RJ" connectors is not twisted pair, and is *not* designed as such
to avoid crosstalk. Randomly and separately pulled through a duct with
other like cables, it may act "twisted", but if the straps are
accidentally or deliberately laid neatly together for any distance you
really are "asking for" crosstalk problems.
This is of course exactly what Chris goes on to describe.
On Tue, 12 May 1998 22:17:39 -0000 Eric Smith <BROUHAHA.COM> writes: eric
>Note that flat modular telephone cable is often wired with a flip
>pin 1 at one end is wired to pin 'n' at the other end. 10BaseT and
>cable has to be "straight-through", unless you're using a crossover
>between two nodes, in which case two pairs get swapped.
Anyone know why telephone line cords are assembled with a "flip"?
Actually, the flip SEEMS like it'd be a great idea for data cables. All
sockets would be wired the same. The swapping of transmit and receive
pairs would happen in the cable flip. You could hook anything to
anything (eliminating the old RS232 DTE/DCE problem).
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]
William Chops Westfield
Actually, the flip SEEMS like it'd be a great idea for data cables.
All sockets would be wired the same. The swapping of transmit and
receive pairs would happen in the cable flip. You could hook anything
to anything (eliminating the old RS232 DTE/DCE problem).
The last round of "rs232 on rj45" pinouts developed at cisco had exactly
this feature. You could plug one end of a (flipped) rj45 flat cable into
one jack and the other end into another jack, and the right wires would be
connected so that everything (data, hw flow control, modem control) worked
right. In addition, the "important" wires were in the middle, so you could
use as small as 4-wire cable for a 3-signal circuit. I thought it was a
It generated quite a bit of complaint and confusion however...
1) Using "standard" wiring schemes, it apparently results in inappropriate
wires being twisted with each other once you get to the twistewd part
of the wiring.
2) While we based this and the db25 adaptors on an existing (flipped)
rj-45 cable assuming that they were "standard", they weren't. At
least one entire product line that uses the same pinout for the rj45
jacks for the "console" and "auxilliary" somehow missed something and
shipped (for a LONG time) with NON-flipped flat cables, and their own
(different) rj45-db25 adaptors. Really confusing things happened if
you tried to move connectors or cables from those products to or from
the "terminal server" products that understood the original pinout.
3) Things get confusing when you try to chain cables together...
More... (looser matching)
- Last day of these posts
- In 1998
, 1999 only
- New search...