What is Cat 5

Cat 5 is a twisted pair high signal integrity cable type, which is often referred to as Category 5. Most of the cables are unshielded relying on the twisted pair design for noise rejection, while some are shielded. Cat 5 has been replaced by the Category 5e specification structured cabling for computer networks, for example, Ethernet, as well as is used to carry many other signals such as basic voice services, token ring, and ATM at up to 155 Mbit/s, over short distances. The specification for cat 5 cable was defined in ANSI/TIA/EIA-568-A, with the clarification in TSB-95. Those documents specify performance characteristics and also test requirements for frequencies of up to 100 MHz.
Cat 5 cable includes twisted pairs in a single cable jacket. The use of balanced lines helps to preserve a high signal to noise ratio in spite of the interference from both external sources and other pairs such as interference from cross talk. It is most commonly used for 100 Mbit/s networks, like 100BASE-TX Ethernet, although IEEE 802.3 ab defines standards for 1000BASE-T - Gigabit Ethernet over cat 5 cable. Cat 5 cable, however, has three twists per inch of each twisted pair of 24 gauge (AWG) copper wires within the cables. The particular category of cable in use, can be identified by the printing on the side of the cable. The cable types, connector types and cabling topologies are strictly defined by TIA/EIA-568-B while 8P8C modular connectors are always used for connecting cat 5 cables.