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Encyclopedia > Twisted pair
Each pair is twisted to decrease interference.

Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources, electromagnetic radiation from the UTP cable, and crosstalk between neighboring pairs. Image File history File links Question_book-3. ... A cable is two or more wires bound together which may be bare or covered or insulated. ... Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a (usually undesirable) disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source. ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... In telecommunication, the term crosstalk (XT) has the following meanings: 1. ...

Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In balanced pair operation, the two wires typically carry equal and opposite signals (differential mode) which are combined by addition at the destination. The common-mode noise from the two wires (mostly) cancel each other in this addition because the two wires have similar amounts of EMI that are 180 degrees out of phase. This results in the same effect as subtraction. Differential mode also reduces electromagnetic radiation from the cable, along with the attenuation that it causes. Transmission lines are generally unbalanced or balanced. ... It has been suggested that this article or section be merged into Low voltage differential signaling. ... It has been suggested that this article or section be merged into Low voltage differential signaling. ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... This article is about Physics. ...

The twist rate (also called pitch of the twist, usually defined in twists per metre) makes up part of the specification for a given type of cable. Where pairs are not twisted, one member of the pair may be closer to the source than the other, and thus exposed to slightly different induced EMF. This article is about the unit of length. ... Electromotive force (emf) is the amount of energy gained per unit charge that passes through a device in the opposite direction to the electric field existing across that device. ...

Where twist rates are equal, the same conductors of different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.

In contrast to FTP (foiled twisted pair) and STP (shielded twisted pair) cabling, UTP (unshielded twisted pair) cable is not surrounded by any shielding. It is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables. For other uses, see Telephone (disambiguation). ... This article or section is in need of attention from an expert on the subject. ... A patch cable or patch cord (sometimes patchcord or patchcable) is an electrical cable, used to connect (patch-in) one electronic device to another for signal routing. ...

## Unshielded twisted pair (UTP) GA_googleFillSlot("encyclopedia_square");

Unshielded twisted pair cable.

Twisted pair cables were first used in telephone systems by Bell in 1881 and by 1900 the entire American network was twisted pair, or else open wire with similar arrangements to guard against interference. Most of the billions of conductor feet (millions of kilometres) of twisted pairs in the world are outdoors, owned by telephone companies, used for voice service, and only handled or even seen by telephone workers. The majority of data or Internet connections use those wires. For other uses, see Telephone (disambiguation). ... Alexander Graham Bell (3 March 1847 - 2 August 1922) was a Scottish scientist, inventor and innovator. ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... A landline or main line is a telephone line which travels through a solid medium, either metal wire or optical fibre. ... A landline or main line is a telephone line which travels through a solid medium, either metal wire or optical fibre. ...

UTP cables are not shielded. This lack of shielding results in a high degree of flexibility as well as rugged durability. UTP cables are found in many ethernet networks and telephone systems. For indoor telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T. A typical subset of these AD1L colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables. Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... The 25 pair color code is a color code used to identify individual conductors in a kind of electrical communication wiring known as twisted pair cables. ... This article is about the current AT&T. For the 1885-2005 company, see American Telephone & Telegraph. ...

For urban outdoor telephone cables containing hundreds or thousands of pairs, different twist rates for each pair are impractical. For this design, the cable is divided into smaller but identical bundles, with each bundle consisting of twisted pairs that have different twist rates. The bundles are in turn twisted together to make up the cable. Because they reside in different bundles, twisted pairs having the same twist rate are shielded by physical separation. Still, pairs having the same twist rate within the cable will have greater crosstalk than pairs of different twist rate. Thus to minimize crosstalk within a large cable, careful pair selection is important. Twisted pair cabling is often used in data networks for short and medium length connections because of its relatively lower costs compared to fiber and coaxial cabling. Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... Coaxial Cable For the weapon, see coaxial weapon. ...

### Uses

Unshielded twisted pair (UTP) cabling, because of its 100-year history of use by telephone systems, both indoors and out, is also the most common cable used in computer networking. It is a variant of twisted pair cabling. UTP cables are often called ethernet cables after Ethernet, the most common data networking standard that utilizes UTP cables. For other uses, see Cable (disambiguation). ... For other uses, see Telephone (disambiguation). ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... A landline or main line is a telephone line which travels through a solid medium, either metal wire or optical fibre. ... This article or section is in need of attention from an expert on the subject. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ...

#### Historical note

Wire transposition on top of pole.

Soon after the invention of the telephone, open wire lines were used for transmission. Two wires, strung on either side of cross bars on poles, share the route with electrical power lines. At first, interference from power lines limited the practical distance for telephone signals. Discovering the cause, engineers devised a method, called wire transposition, to cancel out the interference, where once every several poles, the wires crossed over each other. In this way, the two wires would receive similar EMI from power lines. Today, such open wire lines with periodic transpositions can still be found in rural areas. This represented an early implementation of twisting with a twist rate of about 4 twists per kilometre. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For other uses, see Telephone (disambiguation). ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a (usually undesirable) disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source. ... â€œkmâ€ redirects here. ...

## Cable shielding

S/STP, also known as S/FTP.

Twisted pair cables are often shielded in attempt to prevent electromagnetic interference. Because the shielding is made of metal, it may also serve as a ground. However, usually a shielded or a screened twisted pair cable has a special grounding wire added called a drain wire. This shielding can be applied to individual pairs, or to the collection of pairs. When shielding is applied to the collection of pairs, this is referred to as screening. The shielding must be grounded for the shielding to work. Electromagnetic shielding is the process of limiting the flow of electromagnetic fields between two locations, by separating them with a barrier made of conductive material. ... Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a (usually undesirable) disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source. ...

Foiled Twisted Pair cable.

### Shielded twisted pair (STP)

STP cabling includes metal shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interferences). e.g. the 150 ohm shielded twisted pair cables defined by the IBM Cabling System specifications and used with token ring networks. Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ...

### Screened shielded twisted pair (S/STP)

S/STP cabling, also known as Screened Fully shielded Twisted Pair (S/FTP), [1] is both individually shielded (like STP cabling) and also has an outer metal shielding covering the entire group of shielded copper pairs (like S/UTP). This type of cabling offers the best protection from interference from external sources.

### Screened unshielded twisted pair (S/UTP)

S/UTP, also known as Fully shielded (or Foiled) Twisted Pair (FTP), is a screened UTP cable.

## Advantages

• It is a thin, flexible cable that is easy to string between walls.
• Because UTP is small, it does not quickly fill up wiring ducts.
• UTP costs less per foot than any other type of LAN cable.

## Disadvantages

• Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance.

Electromagnetic interference (or EMI, also called radio frequency interference or RFI) is a (usually undesirable) disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source. ...

## Minor twisted pair variants

• Nonloaded twisted pair: A twisted pair that has no intentionally added inductance. Wires that go more than a mile (1.6 km) usually have load coils to increase their inductance, unless they are to carry higher than voiceband frequencies.

An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Î¦ through the circuit. ... In electronics, a loading coil is a coil (inductor) that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. ... In electronics, voiceband means the typical human hearing frequency range that is from 20Hz to 20KHz. ...

## See also

In telecommunications, a balanced line or balanced signal pair is a transmission line consisting of two conductors in the presence of ground, which relies on balanced impedances to minimize interference. ... This article does not cite any references or sources. ... Twisted-pair cable used with 10BASE-T 8P8C plug used with 10BASE-T There are several standards for Ethernet over twisted pair or copper-based computer networking physical connectivity methods. ... A registered jack (RJ) is a standardized physical interface for connecting telecommunications equipment (commonly, a telephone jack) or computer networking equipment. ... TIA/EIA-568-B is a set of three telecommunications standards from the Telecommunications Industry Association, a 1988 offshoot of the EIA. The standards address commercial building cabling for telecom products and services. ... Cat5 patch cable Category 5 cable, commonly known as Cat 5, is a twisted pair cable type designed for high signal integrity. ...

## References

Results from FactBites:

 What is twisted pair? - a definition from Whatis.com (514 words) This is known as shielded twisted pair (STP). Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible for you to add another line (perhaps for modem use) when you need it. Although twisted pair is often associated with home use, a higher grade of twisted pair is often used for horizontal wiring in LAN installations because it is less expensive than coaxial cable.
More results at FactBites »

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