What is Cat-5 Cable?

Cat-5 cable, sometimes called Ethernet cable, is short for Category 5 cable, a current industry standard for network and telephone wiring. This type of cable is an unshielded wire containing four pairs of 24 gauge twisted copper pairs, terminating in an RJ-45 connector. If a wire is Cat-5 certified and not just twisted-pair wire, it will have that designation printed on the outside.

Cat 5 cable with RJ45 plug.

The outer casing of this type of cable can come in a variety of colors, with bright blue being quite common. Inside, the twisted pairs are also plastic coated with a standard color scheme: solid orange, blue, green and brown wires twisted into pairs that are white and striped with a solid color. Twisted pairs reduce interference and crosstalk and should be left twisted except at the termination point. Some experts recommend untwisting only 12.7 mm (0.5 in.) of the pairs to separate and make connections. Cat-5 cable can be purchased off a spool in varying lengths or purchased pre-cut in standard lengths with RJ-45 connectors already installed.

Cat-5 cables plug into RJ-45 ports, like the ones on the back of this router.

Cat-5 replaces Cat-3 cable, which could only carry data at speeds up to 10 megabits per second (mbps), while the newer standard cable supports data speeds of 100 mbps or more. It can also reach 300 feet (100 meters) and in addition to networks and telephones, it can be used for many other purposes. Cat-5e is an enhanced cable that supports 1000 mbps or gigabit Ethernet, or can be used with 100 Base-T networks for long distance runs of 1,150 feet (350 meters). This type of cable meets a specific standard called “EIA / TIA 568A-5”, which must be stamped on the outer jacket.

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Among Cat-5 cables, there are three different configurations for pinout or wiring the RJ-45 connectors. Various network devices use one of three, which are referred to as direct, cross, and roll-over.

The cable that goes from a computer to a switch will be a straight cable, for example. If two PCs or two switches are connected, a crossover cable will be used. A rollover cable will connect a PC to a router. Newer devices, however, can detect the type of cable being used and route the signals accordingly.

Network cable testers can be used to know if an Ethernet cable is capable of carrying a signal.

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