Microsoft KB Archive/151713

= Description of Twisted-Pair Category Types =

Article ID: 151713

Article Last Modified on 7/16/2004

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APPLIES TO


 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft LAN Manager 2.2c
 * Microsoft Windows for Workgroups 3.11
 * Microsoft TCP/IP for Windows for Workgroups 3.11
 * Microsoft TCP/IP for Windows for Workgroups 3.11a
 * Microsoft TCP/IP for Windows for Workgroups 3.11b
 * Microsoft Windows 95
 * Microsoft Network Client 3.1

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This article was previously published under Q151713



SUMMARY
This article describes twisted-pair cabling and its role in the Electronic Industries Association/Telecommunications Industries Association (EIA/TIA)568 Commercial Building Wiring Standard specification.



MORE INFORMATION
Twisted-pair consists of copper core wires surrounded by an insulator. Two wires are twisted together to form a pair, and the pair forms the circuit that can transmit data. A cable is a bundle of one or more twisted pairs surrounded by another insulator and twisted together. Unshielded twisted-pair (UTP) is common in a telephone network. Shielded twisted-pair (STP) provides protection against external crosstalk by using braided metal shielding. The twisting prevents interference problems, but must be maintained all the way to the connection points.

Categories of Twisted-Pair
The EIA/TIA 568 specification standardizes the installation of wiring. It applies to all UTP wiring schemes that work with Ethernet 10Base-T, token-ring, Private Branch Exchange (PBX), Integrated Services Digital Network (ISDN), and Twisted Pair-Physical Media Dependent (TP-PMD) networks. EIA/TIA 568 defines the following cable categories:

Category 1: Unshielded twisted-pair (UTP) cable that is suited for voice but not data. Most telephone cable installed before 1983 is Category 1 cable. Not widely used anymore.

Category 2: UTP cable certified for data transmissions up to 4 Mbits/second. Similar to IBM Cabling System Type 3 and is commonly installed as modern telephone cable. This cable has four twisted pairs.

Category 3: UTP that supports 10-Mbits/sec transmission rates and is required for token-ring (4 Mbits/sec) and 10-Mbits/sec Ethernet 10Base-T. The cable must have four pairs and three twists per foot.

Category 4: UTP certified for 16 Mbits/sec transmission rates and is the lowest grade acceptable for 16 Mbits/sec token-ring. The cable has four pairs.

Category 5: Defines 100-ohm, four-wire twisted-pair UTP copper cable that can transmit data at 100 Mbits/sec to support technologies such as Fast Ethernet and Asynchronous Transfer Mode (ATM), if installed according to specifications. The cable is low-capacitance and exhibits low crosstalk. However, all components must be Category 5 compliant; therefore, older modular connectors and jacks are not suitable for Category 5 installations.

