TIA/EIA-568-A, T-568B RJ45 Wiring Standard
For wiring straight-through and cross-over RJ-45 cables
RJ-45 conductor data cable contains 4 pairs of wires each consists of a solid colored wire and a strip of the same
color. There are two wiring standards for RJ-45 wiring: T-568A and T-568B. Although there are 4 pairs of wires,
10BaseT/100BaseT Ethernet uses only 2 pairs: Orange and Green.
The two wiring standards are used to create a cross-over cable (T-568A on one end, and T-568B on the
other end), or a straight-through cable (T-568B or T-568A on both ends).
To create a straight-through cable, you'll have to use either T568A or T-568B on both ends of the cable. The diagram depicted on
the left and right shows clip of the RJ-45 connector down.
To create a cross-over cable, you'll wire T-568A on one end and T568B on the other end of the cable.
The straight-through cables are used when connecting Data
Terminating Equipment (DTE) to Data Communications Equipment
(DCE), such as computers and routers to modems (gateways) or
hubs (Ethernet Switches). The cross-over cables are used when
connecting DTE to DTE, or DCE to DCE equipment; such as
computer to computer, computer to router; or gateway to hub
connections. The DTE equipment terminates the signal, while DCE
equipment do not.
How to Build an Ethernet Cable Instructions:
1. Pull the cable off the reel to the desired length and cut using wire cutters or scissors. If you are pulling cables through
holes, it's easier to attach the RJ-45 plugs after the cable is pulled. The total length of wire segments between a PC and a
switch or between two PC's cannot exceed 100 Meters (328 feet) for 100BASETX and 300 Meters for 10BASE-T.
2. Start on one end and strip the cable jacket off (about 1") using a wire stripper or a knife. Be extra careful not to nick
the wires, otherwise you will need to start over.
3. 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.
4. 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 crimp tool.
5. 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:
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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
How to make a Cat 5 Patch Cable
(http://www.warehousecables.com/how-to-make-a-cat5-patch-cable.php)
Cat 5E Patch Cable Assembly Instructions
Step 1: Cut the cable to the length needed.
Step 2: Strip back the cable jacket approximately 1 inch.
Use the cutter provided with the crimping tool or strip by hand.
Be careful not to nick the individual wires.
Un-twist each of the 4 pairs and straighten each wire as much as possible between the fingers.
Step 3: Use the 568-B wiring scheme on both ends for a standard patch cable.
For a crossover type cable use the 568-B scheme on one end and the 568A on the other end.
Step 4: Bring all of the wires together as closely as possible.
Hold the grouped (and sorted) wires together tightly between the thumb, and the forefinger.
Cut all of the wires at a perfect 90 degree angle from the cable,
1/2 inch from the end of the cable jacket.
Use a sharp cutting tool so as not to "squash" the wire ends.
Step 5: With the connector pins facing up, carefully insert the wires into the connector.
Apply a moderate amount of force in order to properly seat the wires against the contacts in the connector.
Step 6: Observe the tip of the connector to confirm that all the wires are fully inserted. The end of each wire you should be in full
view. Also, there should be enough of the cable jacket inside the connector to crimp against. The un-twisted part of the wires CANNOT
exceed 1/2".
Step 7: Place the connector into the crimp tool, and squeeze hard so that the handle reaches its full swing. The crimp tool presses in
the gold plated electrical contact down such that they pierce through insulation of all eight wire and make contact with the copper
conductor. This is called insulation displacement and is why there is no need to strip the insulation off of the individual wires. The other
thing the crimp tool does is press down on a hinged tab that grips onto the cables outer jacket to provide a strain relief action and
helps to keep the cable and the connector intact.
Notice in the photo above how jacketed portion of the cable goes all the way up into the plug. This is right way to do this.
DO NOT leave portions of the cable exposed without a jacket covering it. This jacket is key to keeping the all important
twists in the CATx cable intact and to keep the pairs grouped together.
Step 8: Always use a cable tester to check for continuity, opens and shorts.