By far the most common type of cabling that you’ll come across today, unshielded twisted pair (UTP) cabling originates it the world of voice, being the same type of wiring used for telephone connections. UTP provides a number of advantages over coaxial cable, the main being the flexibility it provides in wiring a network. Instead of having to connect devices along a single length of cable, individual systems can be connected to switches or hubs using a patch cable with RJ45 connectors. UTP is most commonly used to wire Ethernet networks.
UTP cables are made up of pairs of copper wires twisted together. The twisting serves an important purpose – it helps to eliminate electromagnetic interference (EMI). EMI is a common problem on networks using copper wire. Signals from one wire pair might interfere with another (referred to as crosstalk), while powerful external electrical devices may also impact transmission capabilities. When using UTP cables, a common mistake is to unravel the twisting too far – this will certainly degrade signal strength and make the wires more prone to interference.
The category of the cabling defines how many wire pairs you’ll find in a given cable. Voice grade cable, also known as Category (or simply ‘Cat’) 3, uses only two pairs and is used for telephone service and 10Mb Ethernet. Cat 5 wiring, on the other hand, uses 4 wire pairs and is the minimum required for 100Mb Fast Ethernet. For the most part, buildings today are usually pre-wired for Cat 5, although Cat 3 may still be found in older environments. You may also come across what is known as Cat 5E – this version of Cat 5 simply has more twists per inch of wiring, providing better resistance to EMI and higher transmission capabilities.