Cat-3 and Cat-5 Cables
- Cat-3 cable was introduced in the early 1990s and was a popular standard for use in early local area networks, or LANs. The Cat-5 cable replaced the Cat-3 standard for Ethernet usage in the mid-90s due to its abilities to transmit much higher data speeds. However, Cat-3 cable, which is one of the oldest cable standards used for data transmission, has outlived its younger sibling as a standard, due to its lower cost and the introduction of a transmission method that could make use of all four pairs of its internal wires.
- Both Cat-3 and Cat-5 cables are comprised of four twisted pair, for a total of eight 24- gauge copper wires. Both cable standards are unshielded, and both have an outer sheath stamped as certified Cat-3 or Cat-5. Electronic noise that could be experienced along a length of cable carrying such high rates of data transmission is reduced by very precise twisting of the wire pairs. For example, in a Cat-5 cable, the four twisted pairs of wire have six twists per every five centimeters.
Data Transfer Rates
- Cat-3 cable can carry data speeds of up to 10 megabits per second (mbps), while Cat-5 cable supports speeds of 100 mbps or higher. Cat-5 cable can also be used for longer runs, up to 300 feet (100 meters) between computers or switches. Although it may resemble it's faster cousin, Cat-3 cable should only be used for lower speed data transmissions; it can cause errors if it is used in installations requiring faster speeds.
- Cat-3 cable is still used in PBX phone systems and Voice Over Internet Protocol (VoIP) installations, along with the slower 10Base-T Ethernet installations. Cat-5 cable is widely used for 10/100Base-T Internet and analog voice installations. Even though it is newer than Cat-3, Cat-5 is no longer a standard, having been replaced by the Cat-5e specification that supports 1000 megabits, or gigabit Ethernet, and long cable runs of up to 1,150 feet (350 meters).
- Cat-3 saw a resurgence when the 100BaseT-4 standard was devised. The slower 10Base-T Ethernet standard that runs over Cat-3 cable uses only two pair of the available four twisted pair. The 100BaseT-4 standard, which achieves speeds of up to 100 mbps, uses all four pairs of wires within a Cat-3 cable. This allowed businesses that were already wired for Cat-3 to retain their existing wiring, but upgrade to the higher speeds. Cat-3 cable is still popular because it is much less expensive than the Cat-5 and other cable standards rated for higher speeds.