The UTP cable, Unshielded Twisted Pair (UTP), is a balanced, unshielded cable with colored wires twisted in pairs. This type of cable, which comes in two-pair and four-pair versions, was the dominant cable type in floor wiring and terminal cabling in the 1990s. It is part of the 11801 cabling standard and EIA/ TIA specifications.
Due to the development of faster data networks with transmission rates of 1 Gbit/s and higher, there has been a rapid development in UTP and especially STP and FTP cables. New product developments far exceed the specifications of the best UTP cables that existed years ago. The end of the development is not yet in sight, as the theoretical maximum is transmission rates of 950 Mbit/s per cable pair. This would mean that bit rates up to nearly 4 Gbit/s could be transmitted when using four pairs of wires.
Advantages of UTP cables
UTP cables are characterized by their flexibility and low cost, they are easy to install, have a small diameter, low weight and they are easy to handle in terms of connection technology. Thanks to their wide frequency range, they can be used for ISDN, Token Ring, Ethernet, Fast Ethernet, Gigabit Ethernet and for ATM.
UTP usually consists of four-pair 24 AWG (American Wire Gauge) wires sheathed in thin colored insulation. In addition to the unshielded version U/UTP, there are shielded versions: S/UTP with braided shielding, F/UTP with foil shielding and SF/UTP with combined braided/foil shielding.
S/UTP cables have an overall shield for all twisted pairs. Such shielding, as braided or foil shielding, improves the interference radiation properties, but has no influence on the near-end cross-talk attenuation( NEXT).
Characteristic values of UTP cables
Normally, UTP cable has 100 Ohmimpedance, but there are some countries where 120 Ohm impedance is preferred. The impedance may deviate from the nominal value by up to ± 15% over the specified frequency range.
UTP cables are divided into classes for cable standardization. This classification takes into account different applications or frequency ranges. Several standardization bodies have taken on the task of standardization. This has led to different bodies using different classification designations. Underwriters Labs( UL) developed the Level Program in 1989 with Anixter for the classification of UTP cables, defining Levels I, II, III, IV and V. The UL classification was aligned with the EIA/TIA categorysystem and renamed Category by Underwriters Labs. Under Underwriters Labs, there are Categories 1 through 5, with UL Categories 3, 4 and 5 identical to ISO/ IEC 11801 and EN 50173 Categories 3, 4 and 5. In addition, there are Categories 6 and 7 for frequencies up to 250 MHz and 600 MHz, respectively.