Page 101 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Exposure to Computer Disciplines

Notes UTP Cable
UTP cable is a medium that is composed of pairs of wires. UTP cable is used in a variety of
networks. Each of the eight individual copper wires in UTP cable \is covered by an insulating
material. In addition, the wires in each pair are twisted around each other.
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).
To further reduce crosstalk between the pairs in UTP cable, the number of twists in the wire pairs
varies. UTP cable must follow precise specifications governing how many twists or braids are
permitted per meter (3.28 feet) of cable.

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.
When used as a networking medium, UTP cable has four pairs of either 22- or 24-gauge copper
wire. UTP used as a networking medium has an impedance of 100 ohms; this differentiates it from
other types of twisted-pair wiring such as that used for telephone wiring, which has impedance
of 600 ohms.
UTP cable offers many advantages. Because UTP has an external diameter of approximately
0.43 cm (0.17 inches), its small size can be advantageous during installation. Because it has
such a small external diameter, UTP does not fill up wiring ducts as rapidly as other types
of cable. This can be an extremely important factor to consider, particularly when installing
a network in an older building. UTP cable is easy to install and is less expensive than other
types of networking media. In fact, UTP costs less per meter than any other type of LAN
cabling. And because UTP can be used with most of the major networking architectures, it
continues to grow in popularity.

Disadvantages also are involved in using twisted-pair cabling, however. UTP cable is more prone
to electrical noise and interference than other types of networking media, and the distance between
signal boosts is shorter for UTP than it is for coaxial and fiber-optic cables.
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.

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