The specification for Category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95. These documents specified performance characteristics and test requirements for frequencies of up to 100 MHz. Cable types, connector types and cabling topologies are defined by TIA/EIA-568-B. The cable is terminated in either the T568A scheme or the T568B scheme. The two schemes work equally well and may be mixed in an installation so long as the same scheme is used on both ends of each cable. Nearly always, 8P8C modular connectors, often referred to as RJ45, are used for connecting category 5 cable. The USOC/RJ-61 standard is used in multi-line telephone connections.
Each of the four pairs in a Cat 5 cable has differing precise number of twists per metre to minimize crosstalk between the pairs. Although cable assemblies containing 4 pairs are common, Category 5 is not limited to 4 pairs. Backbone applications involve using up to 100 pairs. This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and crosstalk from other pairs. Category 5 cabling is most commonly used for faster Ethernet networks, such as 100BASE-TX and 1000BASE-T.