The information listed here is to assist Network Administrators in
the color coding of Ethernet cables. Please be aware that modifying
Ethernet cables improperly may cause loss of network connectivity. Use
this information at your own risk, and insure all connectors and cables
are modified in accordance with standards. The Internet Centre and its
affiliates cannot be held liable for the use of this information in
whole or in part.
T-568A Straight-Through Ethernet Cable
The
TIA/EIA 568-A standard which was ratified in 1995, was replaced by the
TIA/EIA 568-B standard in 2002 and has been updated since. Both
standards define the T-568A and T-568B pin-outs for using Unshielded
Twisted Pair cable and RJ-45 connectors for Ethernet connectivity. The
standards and pin-out specification appear to be related and
interchangeable, but are not the same and should not be used
interchangeably.
T-568B Straight-Through Ethernet Cable
Both
the T-568A and the T-568B standard Straight-Through cables are used
most often as patch cords for your Ethernet connections. If you require a
cable to connect two Ethernet devices directly together without a hub
or when you connect two hubs together, you will need to use a Crossover
cable instead.
RJ-45 Crossover Ethernet Cable
A
good way of remembering how to wire a Crossover Ethernet cable is to
wire one end using the T-568A standard and the other end using the
T-568B standard. Another way of remembering the color coding is to
simply switch the Green set of wires in place with the Orange set of
wires. Specifically, switch the solid Green (G) with the solid Orange,
and switch the green/white with the orange/white.
Ethernet Cable Instructions:
- Pull
the cable off the reel to the desired length and cut. If you are
pulling cables through holes, its easier to attach the RJ-45 plugs after
the cable is pulled. The total length of wire segments between a PC and
a hub or between two PC's cannot exceed 100 Meters (328 feet) for
100BASE-TX and 300 Meters for 10BASE-T.
- Start on one end and
strip the cable jacket off (about 1") using a stripper or a knife. Be
extra careful not to nick the wires, otherwise you will need to start
over.
- Spread, untwist the pairs, and arrange the wires in the
order of the desired cable end. Flatten the end between your thumb and
forefinger. Trim the ends of the wires so they are even with one
another, leaving only 1/2" in wire length. If it is longer than 1/2" it
will be out-of-spec and susceptible to crosstalk. Flatten and insure
there are no spaces between wires.
- Hold the RJ-45 plug with the
clip facing down or away from you. Push the wires firmly into the plug.
Inspect each wire is flat even at the front of the plug. Check the order
of the wires. Double check again. Check that the jacket is fitted right
against the stop of the plug. Carefully hold the wire and firmly crimp
the RJ-45 with the crimper.
- Check the color orientation, check
that the crimped connection is not about to come apart, and check to see
if the wires are flat against the front of the plug. If even one of
these are incorrect, you will have to start over. Test the Ethernet
cable.
Ethernet Cable Tips:
- A straight-thru cable has identical ends.
- A crossover cable has different ends.
- A straight-thru is used as a patch cord in Ethernet connections.
- A crossover is used to connect two Ethernet devices without a hub or for connecting two hubs.
- A crossover has one end with the Orange set of wires switched with the Green set.
- Odd numbered pins are always striped, even numbered pins are always solid colored.
- Looking at the RJ-45 with the clip facing away from you, Brown is always on the right, and pin 1 is on the left.
- No more than 1/2" of the Ethernet cable should be untwisted otherwise it will be susceptible to crosstalk.
- Do
not deform, do not bend, do not stretch, do not staple, do not run
parallel with power cables, and do not run Ethernet cables near noise
inducing components.
Basic Theory:
By
looking at a T-568A UTP Ethernet straight-thru cable and an Ethernet
crossover cable with a T-568B end, we see that the TX (transmitter) pins
are connected to the corresponding RX (receiver) pins, plus to plus and
minus to minus. You can also see that both the blue and brown wire
pairs on pins 4, 5, 7, and 8 are not used in either standard. What you
may not realize is that, these same pins 4, 5, 7, and 8 are not used or
required in 100BASE-TX as well. So why bother using these wires, well
for one thing its simply easier to make a connection with all the wires
grouped together. Otherwise you'll be spending time trying to fit those
tiny little wires into each of the corresponding holes in the RJ-45
connector.
நாட்டின் மிக பெரிய லஞ்ச ஊழல் நடமாடும் வட்டார போக்குவரத்து கழகத்தின் (RTO) ஆன் லைன் சர்வீஸ் செயல்ப்படும். 
