Guided Media Transmission

Twisted Pair Cable

In twisted pair technology, two copper wires are strung between two points. The two wires are typically ``twisted'' together in a helix to reduce interference between the two conductors. Twisting decreases the crosstalk interference between adjacent pairs in a cable.

Typically, a number of pairs are bundled together into a cable by wrapping them in a tough protective sheath. Can carry both analog and digital signals. Actually, they carry only analog signals. However, the “analog'” signals can very closely correspond to the square waves representing bits, so we often think of them as carrying digital data.

Use: The oldest and the most popular use of twisted pair are in telephony. In LAN it is commonly used for point-to-point short distance communication (say, 100m) within a building or a room.

There are two types of Twisted Pair cables. These are the Unshielded Twisted Pair and Shielded Twisted Pair.

Unshielded Twisted Pair (UTP):

This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.

Advantages:

Least expensive
Easy to install
High speed capacity

Disadvantages:

Susceptible to external interference
Lower capacity and performance in comparison to STP
Short distance transmission due to attenuation

Shielded Twisted Pair (STP):

This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.

Advantages:

Better performance at a higher data rate in comparison to UTP

Eliminates crosstalk

Comparitively faster

Disadvantages:

Comparitively difficult to install and manufacture

More expensive

Bulky