Twisted pair

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It has been suggested that Unshielded twisted pair be merged into this article or section. (Discuss)

Twisted pair cabling is a form of wiring in which two conductors are wound around each other for the purposes of canceling out electromagnetic interference from external sources and crosstalk from neighbouring wires. The twist rate (usually defined in twists per meter) makes up part of the specification for a given type of cable. The greater the number of twists, the more crosstalk is reduced.

Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced as much as physically possible. Often the two wires carry equal and opposite signals which are combined by subtraction at the destination. The noise from the two wires cancel each other in this subtraction because the two wires have been exposed to similar electromagnetic interference.

1 Uses
- 1.1 UTP Cables
2 Cable Shielding
3 See also
4 External links

[edit] Uses

Twisted pair cabling headed with a registered jack

[edit] UTP Cables

Twisted pair cables were first used in telephone systems by Bell in 1881 and by 1900 the entire American network was twisted pair.

In 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.

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.

[edit] Cable Shielding

Main article please see Electromagnetic shielding.

Twisted pair cables are often shielded to prevent electromagnetic interference. Because the shielding is made of metal, it also serves as a ground. 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.

[edit] Unshielded Twisted Pair (UTP)

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.

[edit] 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.

[edit] 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.

[edit] Screened Unshielded Twisted Pair (S/UTP)

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

Screened Unshielded Twisted Pair, Foiled Twisted Pair, Screened Foiled Twisted Pair

[edit] See also

[edit] External links

Unshielded Twisted Pair Cabling Standards

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Cat 1: Currently unrecognized by TIA/EIA. Previously used for POTS telephone communications, ISDN and doorbell wiring.
Cat 2: Currently unrecognized by TIA/EIA. Previously was frequently used on 4 Mbit/s token ring networks.
Cat 3: Currently defined in TIA/EIA-568-B, used for data networks utilizing frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.
Cat 4: Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.
Cat 5: Currently unrecognized by TIA/EIA. Provided performance of up to 100 MHz, and was frequently used on 100 Mbit/s ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.
Cat 5e: Currently defined in TIA/EIA-568-B. Provides performance of up to 100 MHz, and is frequently used for both 100 Mbit/s and gigabit ethernet networks.
Cat 6: Currently defined in TIA/EIA-568-B. It provides performance of up to 250 MHz, more than double category 5 and 5e.
Cat 7: An informal name applied to ISO/IEC 11801 Class F cabling. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Designed for transmission at frequencies up to 600 MHz.