5 things most installers don’t know about Cat 5/5E/6 network cables


For the prevalence of Cat 5/5E/6 cables darting their way through the walls and floors of buildings across the world to carry the microscopic packets of information, some of us are not as familiar with these wires of wonder as we should be. To help acquaint you with a network technician’s best friend and most aggravating foe, here are five facts about Ethernet cables that every tech should know.

1. Twisted Pairing

The twists in the wires throughout the cables take advantage of a property called common-mode rejection. Electromagnetic waves and other signals can induce small variations in the signal. Through twisting the pairs, each receives the same levels of noise. By pairing the information from the two wires together, the noise can be identified and removed to allow a clear 1 or a 0 to show for the receiving end. As little as 1/2 an inch of untwisted Ethernet can fall prey to cross-talk. Without this feature, we would need much more stringent error checking processes that would slow down all of our networking technology.

2. To Shield or Not to Shield

Unshielded Ethernet cables won’t be disrupted by minor radio waves and electronic transmissions in the surrounding area, but areas with a lot of interference can induce signal noise even through the rubber exterior. When you happen to be setting up a network in one of these areas, a metal foil is added around the wires to help shield them. Unless specifically needed, Shielded Twisted Pair (STP) offers no benefits over Unshielded Twisted Pair (UTP).

3. Color Coordination

The color of the wires within the Ethernet cable help identify their position and pairing. Two standards govern the matching between the color and the slot the wire fills: T-568A and T-568B. Each features a mix of solid color and the same color slashed with white that constitute a twisted pair.  From position 1 to 8 with the common abbreviation in parentheses, T-568A is: (g) green with white, (G) green, (o) orange with white, (B) blue, (b) blue with white, (O) orange, (br) brown with white, and (BR) brown. T-568B colors are: (o) orange with white, (O) orange, (g) green with white, (B) blue, (b) blue with white, (G) green, (br) brown with white, and (BR) brown.

4. He’s Going for Distance

Despite the millions of miles of Cat 5/5E/6 cable in use, each individual segment is shorter than 100 meters. Many of the wires are even shorter due to the degradation and attenuation of the signal over longer wires. Simply put, the extra length provides more room for outside signals to invade the low voltages used by data transmission and surpass the error checking capabilities of the network devices.

5.  Too Much Voltage

It is fundamental knowledge that the Ethernet cables allow electrons to travel from one device to another, but do you know how strong the signal is and how high it can be?  In normal IP operations, the voltage will vary between -2V and +2V in increments of 1. Switching over to Power over Ethernet lets you tap into more electrons to energize devices without extending or modifying the actual electrical wiring of the building. In this mode, the Ethernet cable will carry up to 57 volts for a maximum power delivery of 30 watts.

A Cat 5/5E/6 Is a Tech’s Best Friend

Now that you know a little more about Ethernet cables, continue your education with information on how to test and work with the ones that exist in your clients’ networks.