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. Canada and Australia use the T568A standard, and the United Kingdom & United States commonly uses 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 incorrectly referred to as "RJ-45", 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 based on prime numbers to minimize crosstalk between the pairs. On average there are 6 twists per 5 centimetres. The pairs are made from 24 gauge (AWG) copper wires within the cables.
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.
The cable is available in both stranded and solid conductor forms. The stranded form is more flexible and withstands more bending without breaking and is suited for reliable connections with insulation piercing connectors, but makes unreliable connections in insulation-displacement connectors (IDCs). The solid form is less expensive and makes reliable connections into insulation displacement connectors, but makes unreliable connections in insulation piercing connectors.
Taking these things into account, building wiring (for example, the wiring inside the wall that connects a wall socket to a central patch panel) is solid core, while patch cables (for example, the movable cable that plugs into the wall socket on one end and a computer on the other) are stranded. Outer insulation is typically PVC or LSOH. The specific category of cable in use can be identified by the printing on the side of the cable.