Q: Concerning Category 3, 4, and 5 cables used in Ethernet applications, what is the number of twists in Category 3, 4, and 5 cables? Do Category 3, 4, and 5 use the same type of copper? What is the diameter of Category 3, 4, and 5 cables? What type of plastics are used to jacket twisted pairs and twisted-pair cables?
Chris Gong
Zeitnet Inc.
Santa Clara, CA
A: Category 3, 4, and 5 cable consists of 24 AWG [American Wire Gauge] thermoplastic-insulated solid conductors formed into four individually twisted pairs and enclosed by a thermoplastic jacket. These cables must meet all requirements of ansi/icea S-80-576, a manufacturing standard developed by the Insulated Cable Engineers Association under the aegis of the American National Standards Institute (ansi--New York, NY), that are applicable to pair inside-wiring cable for plenum or general cabling within a building. Regardless of the category, the diameter of the completed 4-pair cable must be less than 6.35 mm (1/4 inch). The pair twist lengths are selected by the manufacturer to ensure compliance with crosstalk requirements. For additional information, I suggest that you read the ansi/tia/eia-568a, Commercial Building Telecommunications Cabling Standard (October 1995), Section 10. To purchase this standard of the Telecommunications Industry Association (Arlington, VA), contact Global Engineering Documents, 15 Inverness Way, Englewood, CO 80112-5704, or call (800) 854 7179--internationally (303) 397-7956.
Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: [email protected].