Tutorial - Terminating Ethernet cables

Ethernet connections typically use Category 5e or Category 6 cable, which contains four pairs of unshielded twisted pair (UTP) wire. These are terminated using the RJ-45, 8-pin modular connector. The connector pins are designed to penetrate the insulation of each cable when pressure is applied using a compression tool. Here’s how to do it properly...

The insulation on the wires within Cat5/6 cable varies in colour. There are specific colour codes associated with terminating the modular connector to Ethernet standards, of which there are two different ones that may be in use in any given facility. The most commonly used is T568B, the other is T568A (See fig. 1). When terminating cable it is vital you first ascertain which standard is in use on your site. A Solid colour wire and striped colour wire with the same colour are considered a pair, and are twisted together within the cable jacket (See fig.1). It is very important that these cables retain the twisting as close to the connector as possible when terminating. When terminating, you should be aware that there are different cable styles and that you should use the matching crimping tools, modular connector and cable to ensure correct connections.

A. Strip the outer cable jacket. (It is easier to strip off more jacket than necessary and then trim the conductors to the proper length.)

B. Untwist the individual pairs of wires. In some high-quality category cables, the two conductors are bonded together, so you will have to split them apart to use them. You can use snips, a knife, a razor blade or the appropriate splitting tool from the cable company (See fig. 2).

C. Straighten the wires and trim them to the appropriate length. Maintain the original twisting of the pairs as far as possible up to the connector. No more than about 12.5mm of a twisted pair may be untwisted for a Cat5e cable, or the performance at high bit rates will suffer.

D. Insert each wire into the appropriate contact point. Be careful because the orange and brown can look similar. When you insert the connector properly all eight conductors should make it all the way to the end of the connector. Ensure the jacket is inside the connector to provide strain relief.

E. Insert the connector into the crimping tool. Press the handle of the crimper and the pins in the connector will displace the insulation on each wire, making contact with the conductor (See fig. 3).

F. After completing the cable, test it for continuity. It is essential to test each cable you terminate before it is installed to ensure system reliability. This can be done with a simple handheld tool. By plugging both ends of the cable into the device, the tester will indicate pin to pin continuity or shorts. In the event you are testing an installed cable, another tester is required. A more sophisticated piece of equipment will check both the cable’s ability to pass a signal and the amount of noise that may be on the cable by measuring the cross talk.

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