Wednesday, January 28, 2009
How to make a Network Cable
The steps below are general Ethernet Category 5 (commonly known as Cat5) cable construction guidelines. In this example, we will be making a Category 5 cable, but the same general method will work for making any category of network cables.
Unroll the required length of network cable and add a little extra, just in case. If a boot is to be fitted, do so before stripping away the sleeve and ensure the boot faces the correct way.
Carefully remove the outer jacket of the cable, exposing about 1 1/5 inch of the twisted pairs. Be careful when stripping the jacket as to not nick or cut the internal wiring. After removing the outer case, you will notice 8 wires twisted in 4 pairs. Each pair will have one wire of a certain color and another wire that is white with a colored stripe matching its partner (this wire is called a tracer). Sometimes a rip cord (white thread) is also present.
Untwist the pairs so they will lay flat between your fingers. The white piece of thread can be cut off even with the jacket and disposed. For easier handling, cut the wires so that they are 3/4" (19 mm) long from the base of the jacket.
Arrange the wires based on the wiring specifications you are following. There are two methods set by the TIA 568A and 568B. Which one you use will depend on what is being connected. A straight-through cable is used to connect two different-layer devices (e.g. a hub and a PC). Two like devices normally require a cross-over cable. The difference between the two is that a straight-through cable has both ends wired identically, while a cross-over cable has one end wired 568A and the other end wired 568B. For our demonstration in the following steps, we will use 568B, but the instructions can easily be adapted to 568A.
568B - Put the wires in the following order, from left to right:
White orange/ orange/ white green/ blue/ white blue/ green/ white brown/ brown
568A - Put the wires in the following order, from left to right:
White green/ green/ white orange/ blue/ white blue/ orange/ white brown/ brown
Press all the wires flat and parallel between your thumb and forefinger. Verify the colors have remained in the correct order. Cut the top of the wires even with one another so that they are 1/2" (12.5 mm) long from the base of the jacket, as the jacket needs to go into the 8P8C connector by about 1/8", meaning that you only have a 1/2" of room for the individual cables. Leaving more than 1/2" untwisted can jeopardize connectivity and quality. Ensure that the cut leaves the wires even and clean; failure to do so may cause the wire not to make contact inside the jack and could lead to wrongly guided cores inside the plug.
Keep the wires flat and in order as you push them into the RJ-45 plug with the flat surface of the plug on top. The white/orange wire should be on the left if you're looking down at the jack. You can tell if all the wires made it into the jack and maintain their positions by looking head-on at the plug. You should be able to see a wire located in each hole, as seen at the bottom right. You may have to use a little effort to push the pairs firmly into the plug. The cabling jacket should also enter the rear of the jack about 1/4" (6 mm) to help secure the cable once the plug is crimped. You may need to stretch the sleeve to the proper length. Verify that the sequence is still correct before crimping.
Place the wired plug into the crimping tool. Give the handle a firm squeeze. You should hear a ratcheting noise as you continue. Once you have completed the crimp, the handle will reset to the open position. To ensure all pins are set, some prefer to double-crimp by repeating this step.
Repeat all of the above steps with the other end of the cable. The way you wire the other end (568A or 568B) will depend on whether you're making a straight-through, rollover, or cross-over cable. Test the cable to ensure that it will function in the field. In addition, with power-over-Ethernet (PoE) making its way into the market place, crossed wire pairs could lead to physical damage of computers or phone system equipment, making it even more crucial that the pairs are in the correct order. A simple cable tester can quickly verify that information for you. Should you not have a network cable tester on hand, simply test connectivity pin to pin.
See also Wiring Code for 10BaseT/ 100BaseT Cable