Category 5 Cable
Introduction
(cat5, cat5e, network cable, data cable)
Category 5 cable, which is commonly known by many names such as cat5, network or data cable, is the most commonly used cabling for computer networks. It's low cost, high reliability and ease of use makes it an ideal solution for many different applications as well.
Cat 5 has been replaced by cat 5e, which is the next specification assigned by the Telecommunications Industry Association, or TIA. While the cable is essentially unchanged, the wiring schemes have been improved to increase efficiency at long distances. These changes relate to the specification T568A, the older specification, and T568B, the newer specification which is ideal to run gigabit networks. The maximum recommended distance to use cat5e cable is 100 meters, or about 328 feet.
Connectors
The most commonly used connector, or end piece, to a cat5 cable is the 8P8C modular connector. This is there the TIA's spec comes into play. The specification creates a standard color scheme to be used so that uniform cables can be created. This minimizes confusion so that bad cables are created less frequently due to mixing the required pairs on each end of the cable. RJ-45 is typically referred to as the connector, however this association is incorrect as it simply refers to the registered jack, which the finished cables would plug into.
T568A Wiring
Pin 1, White/Green
Pin 2, Green
Pin 3, White/Orange
Pin 4, Blue
Pin 5, White/Blue
Pin 6, Orange
Pin 7, White/Brown
Pin 8, Brown
T568B Wiring
Pin 1, White/Orange
Pin 2, Orange
Pin 3, White/Green
Pin 4, Blue
Pin 5, White/Blue
Pin 6, Green
Pin 7, White/Brown
Pin 8, Brown
Click for larger image
Click for larger image
Crossover Cables
A common variant to the regularly wired T568A/B spec is the crossover cable. Crossover cables are usually used to create 'ad-hoc' networks, which connect devices directly and do not go through a switch or hub. This method is becoming less common as most devices support a feature called "auto-sensing" which allows them to detect if they are plugged into another device and make the change automatically. The difference from a standard network/data cable is that one end has on pair crossed, specifically second and sixth wire are swapped.
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Compatibility
Cat 5 cable has been used in computer networks for a long time. The most recent revision of cat 5, called cat 5e is required for a proper gigabit network. T568b is also the recommended wiring scheme for gigabit speeds. This rule applies for crossover cables as well. Gigabit, or 1000 megabits per second is the fastest widely available network topology available. Gigabit is said to be the upper limits of cat 5e cable, which will eventually be phased out for cat 6 cable. Cat 6 is currently available, but wide acceptance has not taken place yet.
Distance Limitations
Standard cat 5 cable has a distance limitation, which is about 100 meters (about 328 feet). Beyond this distance signal loss effects the cables ability to keep a quality connection. Repeaters are normally used for distances beyond this, or a different technology that permits longer distances, like fiber optics.