Twisted-Pair Cables

Twisted-pair cable is a type of cabling that is used for telephone communications and most modern Ethernet networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs.

Two basic types of twisted-pair cable exist:

• Unshielded twisted pair (UTP) and
• Shielded twisted pair (STP)

UTP:-

UTP cable relies solely on the cancellation effect produced by the twisted wire pairs to limit signal degradation caused by electromagnetic interference (EMI) and radio frequency interference (RFI).

 

UTP cable often is installed using a Registered Jack 45 (RJ-45) connector. The RJ-45 is an eight-wire connector used commonly to connect computers onto a local-area network (LAN), especially Ethernets.

 

Although UTP was once considered to be slower at transmitting data than other types of cable, this is no longer true. In fact, UTP is considered the fastest copper-based medium today.

The following summarizes the features of UTP cable:

• Speed and throughput—10 to 1000 Mbps

• Average cost per node—Least expensive
• Media and connector size—Small

• Maximum cable length—100 m (short)

Commonly used types of UTP cabling are as follows:

• Category 1—Used for telephone communications. Not suitable for transmitting data.

• Category 2—Capable of transmitting data at speeds up to 4 megabits per second (Mbps).

• Category 3—Used in 10BASE-T networks. Can transmit data at speeds up to 10 Mbps.
• Category 4—Used in Token Ring networks. Can transmit data at speeds up to 16 Mbps.

• Category 5—Can transmit data at speeds up to 100 Mbps.

• Category 5e —Used in networks running at speeds up to 1000 Mbps (1 gigabit per second [Gbps]).

• Category 6—Typically, Category 6 cable consists of four pairs of 24 American Wire Gauge (AWG) copper wires. Category 6 cable is currently the fastest standard for UTP.

STP:-

Although STP prevents interference better than UTP, it is more expensive and difficult to install. In addition, the metallic shielding must be grounded at both ends. If it is improperly grounded, the shield acts like an antenna and picks up unwanted signals. Because of its cost and difficulty with termination, STP is rarely used in Ethernet networks.

 

The following summarizes the features of STP cable:

• Speed and throughput—10 to 100 Mbps

• Average cost per node—Moderately expensive

• Media and connector size—Medium to large
• Maximum cable length—100 m (short)

When comparing UTP and STP, keep the following points in mind:-

1. The speed of both types of cable is usually satisfactory for local-area distances.
2. These are the least-expensive media for data communication. UTP is less expensive than STP.

3. Because most buildings are already wired with UTP, many transmission standards are adapted to use it, to avoid costly rewiring with an alternative cable type.