Cat 5 Definition

Category 5 cable, commonly known as Cat 5, is a type of cable designed for use in high speed local area networks (LANs).

A LAN is a network that connects computers and other devices in a relatively small area, typically a single building or a group of buildings.

A Cat 5 cable consists of a thin plastic sheathing that contains four twisted pairs of copper wire, typically 24 gauge wire with three twists per inch. The twisting reduces electrical interference and crosstalk. The cables are terminated by eight-contact RJ-45 connectors, the dominant connector type for use on LANs.

Cat 5 supports high frequencies of up to 100 MHz and speeds of up to 1000 megabits per second. It can be used for ATM, token ring, 1000Base-T, 100Base-T and 10Base-T networking. Its predecessors, Cat 1 through Cat 4, are not designed to handle data transmission as effectively; for example, Cat 3 supports only 10 Mbps and Cat 4 supports 20 Mbps.

Cat 5e is an enhanced version of Cat 5 for use with 1000BASE-T (gigabit) networks and for long-distance 100 Base-T links (350 meters, compared with 100 meters for Cat 5). Most cables sold as Cat 5 are actually Cat 5e. The markings on the cable itself reveal the exact type.

Cat 5 straight-through cables and crossover cables are identical except for different arrangements of the wires into the RJ-45 connectors. The former are used to connect a computer to a hub or a switch. The latter are used to directly connect two of the same type of devices, such as two computers, two hubs or two switches. However, most modern hubs and switches either have an uplink port for this purpose, a button to change a port to uplink mode,or one or more ports with an automatic sensing capability, thereby eliminating the need for crossover cables.

Cat 6 cable is suitable for 1000 Base-T Ethernet up to 100 meters. The proposed Cat 7 standard has four individually-shielded pairs inside electromagnetic shielding and is designed for transmission frequencies up to 600MHz and ten-Gigabit Ethernet.

Created September 22, 2005.
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