rj45.txt	Information on RJ45 Connectors

RJ45 connectors are used for 10-baseT and 100-baseT.
This document includes the pinouts of these connectors.

This page was created as there were a lot of questions about 
making RJ45 connectors and RJ45 null-modem connectors.  The source
of most of the information herein was from a series of E-MAILS
on the <A HREF="http://www.redhat.com">redhat list</A>.

Original mail header info:

 Subject: Re: Totally off topic: RJ45 fab
   Date:  Tue, 5 May 1998 11:00:46 -0500
   From:  "Shawn McMahon" <smcmahon@chickasaw.com>
     To:  "Rob Goodwin" <goodrob@shaw.wave.ca>
     CC:  "Redhat List" <redhat-list@redhat.com>

Info on RJ45:

The RJ45 connector is a telco-like connector used for networking.  
This is used for 10-baseT, 100-baseT, and token ring.  There are 
two formats, TIA/EIA T568A (DOE) and TIA/EIA T568B.

I'm sure you'll get lots of replies, but I'm replying too because this
site has a particularly good set of graphics:

http://www.k12.hi.us/~tethree/96-97/course2/RJ45diagram.html


You probably want to use TIA/EIA 568B, which simplifies things with
telco patch panels.

Then if you have a cable with one 568A end (obvious if you look at them)
you automatically know it's a crossover cable.  (One end 568B and one end
568A equals crossover.)

For reference, print that page out on a color printer and put it up on
the wall.  Besides being a good reference, it makes a nifty poster.  :-)

(I'm thinking of finding somebody with an 11" x 17" color printer for
mine.)

Assuming you're looking at the side of the connector WITHOUT the little
tab, 568B wiring is:

    white-orange
    orange
    white-green
    blue
    white-blue
    green
    white-brown
    brown

    w.....b  [tab DOWN]
    h     r
    /     o
    o     w
    r     n
      xxx
      xxx
      wire

Only 4 wires matter for Ethernet (the orange and green pairs) but you
should always wire it properly anyway.

The wires that matter for token ring, BTW, are the green and blue pairs.

It's always ticked me off that it isn't the blue and brown, because then
an Ethernet crossover cable would work as a normal token ring cable, but as
it stands an Ethernet crossover just doesn't do anything with token ring.
You can't crossover token ring.  :-(

For 568A, you just swap the orange and green.  Thus:

    white-green
    green
    white-orange
    blue
    white-blue
    orange
    white-brown
    brown

    w.....b  [tab DOWN]
    h     r
    /     o
    g     w
    r     n
      xxx
      xxx
      wire

As I said, if you make one side 568B and one side 568A, you have a
crossover cable.

Invest in a GOOD crimper.  It's worth the extra money in terms of
aggravation and troubleshooting time.  A good tester is also very
useful and highly recommended.

A lot of diagrams and instructions look at it from the side WITH the
tab. So if you're making a cable, pay attention to which way the directions
you're using run!  In fact, that URL I refer you to above shows it from
the tab side.  Pick one way, and always do it that way.  If you do, in no
time at all you'll have this memorized, trust me.

Be sure to buy some extra connectors and leave your wires a bit long 
as it is very easy to mess up when first making cables.  A very
common mistake is to make the cable upside down (e.g., use a diagram 
for TAB up but make the cable with the TAB down -- oops).

Oh, some instructions will say "white-orange and orange-white" and so on
for all the wires.  "white-orange" is obvious, it's a white wire with a thin
orange stripe around it.  "orange-white" is an orange wire with a thin
white stripe.  It's so thin, you often can't see there's any white at all.
And some wire doesn't have the white stripes at all.  Just remember that the

first word is the important one, if confronted with one of these
confusing sets of documentation.




