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The two main types of computer networking cable are unshielded twisted pair and shielded twisted pair. Unshielded twisted pair (UTP) is the most common type of computer networking cable in use today. It consists of four pairs of eight wires and is connected using an RJ-45 plug that looks like an over-sized telephone connector. UTP is used by the Ethernet networking protocol.
UTP is organized by the Telecommunications Industry Association/Electronics Industry Association (TIA/EIA) into six categories, depending on the data speed it is rated to carry. They range from Category 6, which includes cables deemed capable of sending data as quickly as 1 gigabit per second, to Category 2, which only sends data as quickly as 4 megabits per second. Category 1 is reserved for basic telephone use.
Of these types of cable, only Categories 5, 5e, and 6 are in general use in late 2010. Category 6 cable is the fastest standard for UTP. It differs from Category 5e in that it has better resistance to electrical noise and external interference, also known as crosstalk. Category 5, which isn't restricted to only four pairs but could have up to 100 pairs in a so-called "backbone application," has been superseded by Category 5e. Category 4 is used in Token Ring networks and, as such, is not in general use anymore. Category 3 is still used in some telephone installations and in Power over Ethernet (PoE) applications.
Category 7 cable has been proposed as a standard to allow 10 Gbps data transmission. It is technically a shielded twisted pair (STP) cable, however, and needs a different connector from previous UTP connectors. In November 2010, equipment manufacturers decided to continue using the RJ-45 plug for their 10 Gigabit Ethernet products. Category 7 is not recognized by TIA/EIA.
Shielded twisted pair (STP) computer networking cable is used by the Token Ring networking protocol. It is two pairs of four wires, with a copper braid or metallic shield around the wires. Although it is still being used in some installations, it is being phased out by the growth of Ethernet and UTP computer networking cable. There are some other network cabling types in use, such as fiber-optic cabling; these cables are fairly specialized, however, and they are not in general use in 2010.
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