Page 112 - DMGT505_MANAGEMENT_INFORMATION_SYSTEM

Unit 6: Business Networks and Telecommunications

(pair-to-pair coupling, or crosstalk) and from outside the cable (EMI and RFI). STP usually is Notes
installed with STP data connector, which is created especially for the STP cable. However, STP
cabling also can use the same RJ connectors that UTP uses.

Figure 6.9: Shielded Twisted-Pair Cable

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. STP is primarily used in Europe. The
following summarizes the features of STP cable:
1. Speed and throughput-10 to 100 Mbps
2. Average cost per node-Moderately expensive

3. Media and connector size-Medium to large
4. 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.

!
Caution Although STP prevents interference better than UTP, it is more expensive and
difficult to install.

6.4.2 Coaxial Cable

Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire
made of two conducting elements. One of these elements, located in the center of the cable, is a
copper conductor. Surrounding the copper conductor is a layer of flexible insulation. Over this
insulating material is a woven copper braid or metallic foil that acts both as the second wire in
the circuit and as a shield for the inner conductor. This second layer, or shield, can help reduce
the amount of outside interference. Covering this shield is the cable jacket. (See Figure 6.10)
Coaxial cable supports 10 to 100 Mbps and is relatively inexpensive, although it is more costly
than UTP on a per-unit length. However, coaxial cable can be cheaper for a physical bus topology
because less cable will be needed. Coaxial cable can be cabled over longer distances than twisted-
pair cable.

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