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Q: Computer Networking ( Answered,   2 Comments )
Subject: Computer Networking
Category: Computers > Hardware
Asked by: vicpal-ga
List Price: $5.00
Posted: 12 Feb 2004 17:42 PST
Expires: 13 Mar 2004 17:42 PST
Question ID: 306317
What is the clor-code order to install the strands of CAT05 cable in 8-pin-plugs?
Subject: Re: Computer Networking
Answered By: haversian-ga on 12 Feb 2004 18:22 PST
Good evening vicpal,

There are two types of ethernet cables, straight-through cables (for
connecting a computer to a router, switch, hub, etc), and crossover
cables (for connecting two computers directly together, etc).  New
network cards and some network hardware will automatically detect
whether they need a crossover cable or not, and will compensate
internally, so you can use a crossover cable where a straight-through
cable is actually called for, or vice versa.  The new IBM laptops, Mac
laptops, and Mac desktops (no doubt others as well, but I have
experience with these) do this.

Also, note that 100baseTX only uses 2 pairs, 4 wires, although cat5
has 4 pairs, 8 wires.  If you are going to use your cables for only
100baseTX operation, you can get away with only connecting 4 wires. 
Gigabit/copper, 1000baseTX, requires all 8 wires.  I'll give you the
color codes for 8-wire cables, as these are no more expensive since
the cables and the plugs already have 8 wires - there's little point
leaving some unconnected.

There is a good textual description and table of the color codes to
use here:

There is also a lesson-plan-style document (PDF) at that provides detailed
instructions on making a variety of cables, among them the two you may
be interested in.

You'll see reference to 568A and 568B.  These are the two endings you
can use.  Using the same on both ends (both A or both B) gives a
straight-through cable, and using one A and one B gives a crossover
cable.  Both B is more common than both A, though it really makes no

This site ( ) has a little
diagram showing the wires and the plugs both for 568A and 568B (a
little bit down the page).

If you want the information presented in other ways, search for "cat5
crossover cable color codes" or "cat5 patch cable diagram" or
variations on that theme.

Attaching the connectors so there's good electrical conductivity takes
a bit of practice.  I recommend you make your first few cables longer
than necessary.  That way when one doesn't work you can cut the bad
end off and try again without wasting the whole length of cable.

Have fun!

Subject: Re: Computer Networking
From: supermacman-ga on 12 Feb 2004 20:36 PST
Basically, you have to keep the colour codes on both ends of the cable
the same, for a good-working Cat5 patch cable.

I have heard that using the approved colours minimises electrical and
magnetic interference between signals sent within the wire; however, I
have made tens of cables without following the colour code and they
work perfectly at 100-Base-T. (I have not tried any cables at
1000-Base-T, but my guess is that they'll work fine.)

For mission-critical operations, you should buy your cables, so they
don't fail. For speed-intensive operations, use the standard colours.
For general use, you can match the colours on both ends and you'll do
just fine.

- supermacman-ga
Subject: Re: Computer Networking
From: toddzer-ga on 10 Dec 2004 15:30 PST

Technically the colors are not important, but to prevent picking
interference from outside sources and preventing crosstalk ("echo"
between transmitting and receiving data) it is CRITICAL that the
"pairs" be kept together.  Pins 1&2 must be a pair, pins 3&6 must be a
pair, and the other 4 aren't used for 100 or 10 Mbit but I think they
are for 1000 Mbit.  If you strip the cable a few inches, you'll see
that the white with blue stripe and blue with white strip are twisted
together - this is a pair.  If you split up the pairs, yes short
cables will usually work fine, but long cables or use next to magnetic
fields will be a problem.  The twist in the pairs is effectively
magnetic sheilding preventing both receiving and sending noise.

So, if you just wire straight through without regard to pairs, you'll
be asking for trouble and cause someone down the road great grief. 
I've had to fix some of these that worked "most of the time."

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