Cable is the medium through which information usually moves from on network device to another. There are several types of cable, which are commonly used with LANs. In some cases, a network will utilize only one type of cable while other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.
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Coaxial cable consists of a single conductor at the core, surrounded by an insulating layer, braided metal shielding called braiding, and an outer cover called the sheath or wrapper. Networking signals that the coax cable carries travel over the central conductor; the remaining elements protect coax cable form external influences, whether electrical, mechanical, or environmental. There are other versions of coax called dual-shielded which surround the braided metal shield with an additional layer of metallic foil and quad-shielded which incorporates two layers of foil insulation and two layers of braided metal shield.
Coaxial cable has a broad frequency range. Coaxial cable offers several advantages for LANs. It can be run for longer distances between network nodes than either shielded twisted-pair or unshielded twisted-pair cable. Coaxial cable is less expensive than fiber-optic cable. It has been used for many years for all types of data communication. It is valuable in the transmitting network data over medium to long distances.
Coaxial cable is also used for cable television (CATV). The two most common types of CATV cable include the 75-ohm (impedance) RG-59 (Radio Government-59) and RG-6 (Radio Government-6 Broadband) cables, where RG-59 is used to connect individual homes to a neighborhood RG-6 distribution line. CATV uses heavy-duty, 75-ohm RG-11 (Radio Government-11, thickwire) cables for trunk lines, as well as fiber-optic cable for especially long cable runs, or where extremely large amounts of bandwidth must be aggregated.
