Cat-5 cable, sometimes called Ethernet cable, is short for Category 5 cable, a current industry standard for telephone and network cabling. This type of cable is an unshielded cable that contains four pairs of 24-gauge twisted copper pairs, terminated in an RJ-45 connector. If a cable is Cat-5 certified and not just a twisted pair cable, it will have that designation printed on the outside.
Cat 5 cable with RJ45 plug.
The outer shell of this type of cable can come in a variety of colors, with bright blue being quite common. On the inside, the twisted pairs are also encased in plastic with a standard color scheme: solid orange, blue, green, and brown wires twisted in 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 only untwisting 0.5 in. (12.7 mm) of the pairs to separate them and make connections. Cat-5 cable can be purchased off the reel in various lengths or it can be purchased pre-cut to standard lengths with RJ-45 connectors already installed.
Cat-5 cables connect to 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 of up to 10 megabits per second (mbps), while newer cable standards support data speeds of 100 mbps or more. It can also reach 300 feet (100 meters) and in addition to networks and phones it can be used for many other purposes. Cat-5e is an enhanced cable that supports 1,000 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 complies with a specific standard called “EIA/TIA 568A-5”, which must be stamped on the outer jacket.
Among Cat-5 cables, there are three different configurations for the pinout or wiring of the RJ-45 connectors. Many network devices use one of three, which are called forward, crossover, and passthrough.
The cable going 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. However, newer devices can detect the type of cable being used and route signals accordingly.
Network cable testers can be used to find out if an Ethernet cable is capable of carrying a signal.
