Category Wiring: What You Need to Know
The fundamentals of twisted pair wiring for today's communication technologies.
Twisted pair wiring, in its most common state, consists of four pairs of 24-gauge solid copper wiring. It's called Category wire, with the number following the category indicating the speed at which data can potentially travel.
Most everyone today uses Category 5e wiring, aka Cat 5e, for data, control signals, voice and, increasingly, transmission of video and audio signals. The wire will have a blue and a white-blue pair, an orange and a white-orange pair, a green and a white-green pair and a brown and a white-brown pair of conductors.
The higher the category rating, the more you'll discover variances in the twist rates on the individual pairs. If you were to take your wire stripper and remove the outer overall jacket and then straighten out each of the pairs of wiring found inside, you'd discover that the wire itself is the same thing.
The twisting of the conductors helps increase the speed at which data can travel down the wire. It also is an effective shielding strategy, which, for voice applications, translates to less cross talk between phone lines.
EIA & TIA Standards
Twisted pair wiring is terminated most commonly using standards developed by the Electronics Industry Association and the Telecommunications Industry Association.
These standards are called EIA/TIA 568 A or B. The difference between the two methods is in where the orange/white-orange and green/white-green conductors are placed on the jack or plug.
Traditionally, the data industry has followed the B standard, and the voice trades the A. If you are wiring for residential applications, where it's possible the jack might be used for voice or data in the future, the A scheme makes more sense.
The A scheme places the blue/white-blue and orange/white-orange conductors in the conventional line one and line two position on the jack.
Regardless of which scheme you choose to use, it's important to follow what the associated equipment manufacturers recommend.
This is extremely important on control systems, where a keypad might have a punch down strip on the back, with a RJ45 jack on the equipment end. You'll find the specific recommendation on connection style in the installation manual for the system.
Don't assume that it's an A or B; when in doubt, check.
Things to Keep in Mind
When you're installing Cat 5 or higher wiring, it's important to understand some of the requirements around handling the wire.
If the wire is pulled too hard, cinched too tight or bent at too sharp a radius (to name a few possibilities), the performance of the wire can be affected.
For voice applications, extremely rough handling can lead to breakage of the fragile conductors. This is the concern.
Where some of the more restrictive covenants really have an effect is on data wiring. If you are trying to deliver a network installation to a particular standard, improper handling will lead to troubling loss of potential speed.
Other things to avoid include:
- More than a 25-pound pull on the wire. I myself am not sure how to test that. So, I suggest that if the wire isn't flowing smoothly, you're probably over the pull limit.
- Bending the wire beyond a 1-inch radius.
- Using staples that will compress the wire.
- Cinching your zip ties too taut. Velcro strips are preferred when working with bundles of wiring because, inevitably, you will want to add another length or two of wire after you dress your bundle.
- Overstuffing wire into conduit.