Tech Talk: Heavy Metal
Oct 1, 2006 12:00 PM, By C. William Day
As communication networks advance, people can access information at speeds and accuracy that were unimaginable just a few years ago.
Ethernet wire was developed in the mid 1970s. The first specification was released in 1980 as a 10 Megabit-per-second system. It became known as 10Base5; the 10 refers to the speed (10Mbps), the base refers to a base band system, and the 5 is short for the system's maximum cable length (in this case 500m).
The Institute of Electrical and Electronic Engineers (IEEE) released an official Ethernet standard in 1983, called the IEEE 802.3. In 1985, version 2 (IEEE 802.3a) was released. By 1987, several manufacturers had developed Ethernet equipment that could use twisted-pair telephone cable, and in 1990 the IEEE released the 802.3I Ethernet standard 10BaseT (the T refers to twisted-pair cable). In 1991, the EIA together with the Telecommunications Industry Association (TIA) published the first telecommunications cabling standard called EIA/TIA 568, and the structured cabling system was born. It was based on Category 3 Unshielded Twisted Pair cable (UTP), and was followed a month later by a Technical Systems Bulletin (TSB-36) that specified higher grades of UTP cable, Category 4 and 5 (Cat 4/Cat 5). Cat 5 specified data rates of up to 100MHz; at the time it must have seemed like ample bandwidth for future development, but now Cat 5 has been replaced with CAT 5e (enhanced).
Since 1990, electrical manufacturing associations have redefined wiring product lines and introduced new cables according to a generally agreed-upon set of levels or grades of media:
Cat 3. Currently defined in TIA/EIA-568-B, used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks and now mainly for telephone cables.
Cat 5e. Currently defined in TIA/EIA-568-B. It provides performance of up to 125MHz and is frequently used for 100Mbit/s and gigabit Ethernet networks. CAT 5e specification simply included some additional limits over the CAT5 specification.
Cat 6. Currently defined in TIA/EIA-568-B. It is a cable standard for Gigabit Ethernet and other network protocols that is backward compatible with the Category 5/5e and Category 3 cable standards. Cat 6 features more stringent specifications for crosstalk and system noise. The cable standard is suitable for 10Base-T/100Base-TX and 1000Base-T (Gigabit Ethernet) connections. It provides performance of up to 250 Mhz.
Cat 7. Currently not certified, it is an informal name applied to ISO/IEC 11801 Class F cabling. Cat 7 is a cable standard for Ultra Fast Ethernet and other interconnect technologies that can be made to be backward compatible with traditional Cat 5e and Cat 6 Ethernet cable. When combined with GG-45 connectors, Cat 7 cable is rated for transmission frequencies of up to 600 MHz.
History and the increasing bandwidth requirements of applications suggest that Cat 6 will be a better investment than Cat 5e for new installations.
Day is senior analyst at KBD Planning Group, Young Harris, Ga., a firm specialized in education facilities and technology planning. He can be reached at bday@kbdplanning.com. www.kbdplanning.com
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