It is mostly used for telephone communications and modern Ethernet networks. It consists of pairs of cables that transmit data. The pairs of cables are twisted so as to prevent the cross talk (noise generated by other pairs of cables). Each pair of copper wire is twisted together and is encased in a unique color-coded plastic jacket for insulation. An outer jacket is put encasing all the twisted pair into one single bundle that consists of all the pairs for effective transmission of data. Generally, an RJ-45 connector (discussed in communication links) is connected at the ends of the cable to provide an interface for communication to nodes. There are two types of twisted pair cable:

Unshielded twisted-pair cable (UTP)
Shielded twisted-pair cable (STP)

Unshielded twisted-pair cable (UTP)

It is the most widely used cable in network cabling (Ethernet networks) due to low cost and relatively easy installation. The number of pairs of cables varies between two and four. This type of cable has no insulation against signal degrading EMI (electro-magnetic interference) and RFI (radio frequency interference) except the overall shield jacket for protection form external interference and so solely depends on the noise cancellation effect produced by twists in the cable to limit signal degradation produced by adjacent pairs. UTPs used in computer network with four pairs use RJ-45 connector for connection interface and those used in home telephone system with two pairs use RJ-11 connectors for connection interface.

Advantages of UTP:

It is cheaper than other communication media.
It is easy to install and repair.
It provides good data transmission in short distance networks.

Disadvantages of UTP:

It is more susceptible to crosstalk, EMI and RFI.
It is not suitable for outdoor use and long distance networks.

Shielded twisted-pair cable (UTP)

It is similar to unshielded twisted pair cable except it has better insulation against signal interference. Each pair of wire is wrapped in metallic foil to further reduce noise. The four cables as a whole bundle are then wrapped in an overall metallic foil or braid. With extra insulation STP reduce crosstalk (electrical noise produced by adjacent pairs) and EMI as well as RFI. However, it is more than UTP cable and difficult to install as it requires the metallic shielding to be grounded at both ends. Improper grounding can result in more EMI and RFI due to the shield acting like an antenna catching unwanted signals. It is generally used in areas more susceptible to EMI, RFI and relatively longer distance network than possible to create by UTP.

Advantages of STP

It is less susceptible to EMI, RFI and crosstalk than UTP.
It provides good data transmission in short distance networks.
It is easy to install than other media.

Disadvantages of STP

It is more expensive than UTP.
It is relatively hard to install and repair than UTP.

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