![25 pair color code chart](https://upload.wikimedia.org/wikipedia/commons/3/35/25_pair_color_code_chart.svg)
Twisted pair cabling is a type of wiring used for communications in which two conductors of a single
circuit are twisted together for the purposes of improving
electromagnetic compatibility
Electromagnetic compatibility (EMC) is the ability of electrical equipment and systems to function acceptably in their electromagnetic environment, by limiting the unintentional generation, propagation and reception of electromagnetic energy whic ...
. Compared to a
single conductor or an untwisted
balanced pair
In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other ci ...
, a twisted pair reduces
electromagnetic radiation
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
from the pair and
crosstalk
In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...
between neighboring pairs and improves rejection of external
electromagnetic interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...
. It was invented by
Alexander Graham Bell
Alexander Graham Bell (, born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist and engineer who is credited with patenting the first practical telephone. He also co-founded the American Telephone and Te ...
.
For additional noise immunity, twisted-pair cabling may be
shielded. Cable with shielding is known as shielded twisted pair (STP) and without as unshielded twisted pair (UTP).
Explanation
A twisted pair can be used as a
balanced line
In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other ...
, which as part of a
balanced circuit A balanced circuit is circuitry for use with a balanced line or the balanced line itself. Balanced lines are a common method of transmitting many types of electrical communication signals between two points on two wires. In a balanced line the tw ...
can greatly reduce the effect of noise currents induced on the line by coupling of electric or magnetic fields. The idea is that the currents induced in each of the two wires are very nearly equal. The twisting ensures that the two wires are on average the same distance from the
interfering source and are affected equally. The noise thus produces a
common-mode signal Common-mode signal is the voltage common to both input terminals of an electrical device. In telecommunication, the common-mode signal on a transmission line is also known as longitudinal voltage.
In most electrical circuits the signal is transfer ...
which can be cancelled at the receiver by detecting the difference signal only, the latter being the wanted signal.
Common-mode rejection
In electronics, the common mode rejection ratio (CMRR) of a differential amplifier (or other device) is a metric used to quantify the ability of the device to reject common-mode signals, i.e. those that appear simultaneously and in-phase on both i ...
starts to fail on untwisted wires when the noise source is close to the signal wires; the closer wire will couple with the noise more strongly and the receiver will be unable to eliminate it. This problem is especially apparent in telecommunication cables where pairs in the same cable lie next to each other for many miles. Twisting the pairs counters this effect as on each half twist the wire nearest to the noise-source is exchanged. Provided the interfering source remains uniform, or nearly so, over the distance of a single twist, the induced noise will remain common-mode.
The twist rate (also called ''pitch'' of the twist, usually defined in twists per
metre
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its pref ...
) makes up part of the specification for a given type of cable. When nearby pairs have equal twist rates, the same conductors of the different pairs may repeatedly lie next to each other, partially undoing the benefits of twisting. 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 shielded or foiled twisted pair (typically S/FTP or F/UTP
cable shielding), UTP cable is not surrounded by any shielding. UTP is the primary wire type for
telephone
A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...
usage and is very common for
computer networking
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ma ...
.
History
![Wire Transposition](https://upload.wikimedia.org/wikipedia/commons/d/d9/Wire_Transposition.svg)
The earliest telephones used telegraph lines which were
single-wire earth return
Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line which supplies single-phase electric power from an electrical grid to remote areas at lowest cost. Its distinguishing feature is that the earth (or ...
circuits. In the 1880s electric
tram
A tram (called a streetcar or trolley in North America) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport are ...
s were installed in many cities, which induced noise into these circuits. In some countries, the tram companies were held responsible for disruption to existing telegraph lines and had to pay for remedial work. For new installations, however, it was necessary to protect against existing trams from the outset. Interference on telephone lines is even more disruptive than it is on telegraph lines. Telephone companies converted to
balanced circuit A balanced circuit is circuitry for use with a balanced line or the balanced line itself. Balanced lines are a common method of transmitting many types of electrical communication signals between two points on two wires. In a balanced line the tw ...
s, which had the incidental benefit of reducing
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...
, hence increasing range.
As electrical power distribution became more commonplace, this measure proved inadequate. Two wires, strung on either side of cross bars on
utility pole
A utility pole is a column or post typically made out of wood used to support overhead power lines and various other public utilities, such as electrical cable, optical fiber, fiber optic cable, and related equipment such as Distribution transfor ...
s, shared the route with electrical
power line
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
s. Within a few years, the growing use of electricity again brought an increase of interference, so engineers devised a method called
wire transposition
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is co ...
, to cancel out the interference.
In wire transposition, the wires exchange position once every several poles. In this way, the two wires would receive similar
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British transnational conglomerate founded in March 1931 in London. At the time of its break-up in 201 ...
from power lines. This represented an early implementation of twisting, with a twist rate of about four twists per
kilometre
The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is now the measurement unit used for ex ...
, or six per
mile
The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English ...
. Such open-wire balanced lines with periodic transpositions still survive today in some rural areas.
Twisted-pair cabling was invented by
Alexander Graham Bell
Alexander Graham Bell (, born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist and engineer who is credited with patenting the first practical telephone. He also co-founded the American Telephone and Te ...
in 1881. By 1900, the entire American telephone network was either twisted pair or open wire with transposition to guard against interference. Today, most of the millions of kilometres of twisted pairs in the world are outdoor landlines, owned and maintained by telephone companies, used for voice service.
Unshielded twisted pair
![UTP-cable](https://upload.wikimedia.org/wikipedia/commons/d/d6/UTP-cable.svg)
Unshielded twisted pair (UTP) cables are found in many
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
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
The 25-pair color code, originally known as even-count color code, is a color code used to identify individual conductors in twisted-pair wiring for telecommunications.
Color coding
With the development of new generations of telecommunication cab ...
originally developed by
AT&T Corporation
AT&T Corporation, originally the American Telephone and Telegraph Company, is the subsidiary of AT&T Inc. that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agen ...
. A typical subset of these colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables. The cables are typically made with
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
wires measured at 22 or 24
American Wire Gauge (AWG), with the colored insulation typically made from an insulator such as
polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
or
FEP and the total package covered in a
polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
jacket.
For urban outdoor telephone cables containing hundreds or thousands of pairs, the cable is divided into small but identical bundles. Each bundle consists of twisted pairs that have different twist rates, as pairs having the same twist rate within the cable can still experience some degree of
crosstalk
In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...
. The bundles are in turn twisted together to make up the cable.
![UTP cable](https://upload.wikimedia.org/wikipedia/commons/c/cb/UTP_cable.jpg)
UTP is also the most common cable used in
computer networking
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ma ...
. Modern
Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
, the most common data networking standard, can use UTP cables, with increasing data rates requiring higher specification variants of the UTP cable. Twisted-pair cabling is often used in data networks for short and medium-length connections because of its relatively lower costs compared to
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...
and
coaxial cable
Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...
.
As UTP cable
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
has improved to match the
baseband
In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into a ...
of
television
Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
signals, UTP is now used in some
video
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
applications, primarily in
security camera
A closed-circuit television camera can produce images or recordings for surveillance or other private purposes. Cameras can be either video cameras, or digital stills cameras. Walter Bruch was the inventor of the CCTV camera. The main purpose o ...
s. As UTP is a balanced transmission line, a
balun
A balun (from "balanced to unbalanced", originally, but now dated from "balancing unit") is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. A balun c ...
is needed to connect to unbalanced equipment, for example any using
BNC connector
The BNC connector (initialism of "Bayonet Neill–Concelman") is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It is designed to maintain the same characteristic impedance of the cable, with 50 ohm and ...
s and designed for coaxial cable.
Cable shielding
![10G BASE-T x 3 cables](https://upload.wikimedia.org/wikipedia/commons/0/03/10G_BASE-T_x_3_cables.svg)
Twisted pair cables may incorporate
shielding in an attempt to prevent electromagnetic interference. Shielding provides an electrically conductive barrier to attenuate electromagnetic waves external to the shield. The shield also provides a conduction path by which induced currents can be circulated and returned to the source via ground reference connection. Such shielding can be applied to individual pairs or to a collection of pairs. Shielding may be foil or braided wire.
When shielding is applied to a collection of pairs, it is usually referred to as screening, but usage among vendors and authors in applying such words as ''screening'', ''shielding'', and ''STP (shielded twisted pair)'' can be subject to variability.
[Anitech Systems MP 4000 Manual](_blank)
/ref>[Grounding for Screened and Shielded Network Cabling - Siemon](_blank)
/ref> ISO/IEC 11801
International standard ISO/IEC 11801 ''Information technology — Generic cabling for customer premises'' specifies general-purpose telecommunication cabling systems (structured cabling) that are suitable for a wide range of applications (analog an ...
:2002 (Annex E) attempts to internationally standardize the various designations for shielded cables by using combinations of three letters - U for unshielded, S for braided shielding (in outer layer only), and F for foil shielding - to explicitly indicate the type of screen for overall cable protection and for protecting individual pairs or quads, using a two-part abbreviation in the form of ''x/xTP''.
Shielded Cat 5e
Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is ...
, Cat 6/6A, and Cat 8/8.1 cables typically have F/UTP construction, while shielded Cat 7/7A and Cat 8.2 cables use S/FTP construction.
Because the shielding is conductive, it may also serve as a path to ground. A foil-shielded, twisted pair cable may have an integrally incorporated grounding wire called a ''drain wire'' which makes electrical contact with the shield. The purpose of the drain wire is for easy connection to terminals which are usually designed for connection of round wires.
Common shield construction types include:
; Individual shield (U/FTP): Individual shielding with aluminum foil for each twisted pair or quad. Common names: pair in metal foil (PiMF), shielded twisted pair, screened twisted pair. This type of shielding helps prevent EMI from entering or exiting individual pairs and also protects neighboring pairs from crosstalk.
; Overall shield (F/UTP, S/UTP, and SF/UTP): Overall foil, braided shield or braiding with foil across all of the pairs within the 100 ohm twisted pair cable. Common names: foiled twisted pair, shielded twisted pair, screened twisted pair. This type of shielding helps prevent EMI from entering or exiting the cable.
; Individual and overall shield (F/FTP, S/FTP, and SF/FTP): Individual shielding using foil between the twisted pair sets, and also an outer foil or braided shielding. Common names: fully shielded twisted pair, screened foiled twisted pair, shielded foiled twisted pair, screened shielded twisted pair, shielded screened twisted pair. This type of shielding helps prevent EMI from entering or exiting the cable and also protects neighboring pairs from crosstalk.
An early example of shielded twisted-pair was IBM STP-A, which is a two-pair 150 ohm S/FTP cable defined in 1985 by the IBM Cabling System specifications, and used with Token Ring
Token Ring network
IBM hermaphroditic connector with locking clip. Screen contacts are prominently visible, gold-plated signal contacts less so.
Token Ring is a computer networking technology used to build local area networks. It was introduc ...
or FDDI networks.
Types
Analog telephone
Before digital communication and Ethernet became widespread there was no international standard for telephone cable. Standards were set at a national level. For instance, in the UK the General Post Office
The General Post Office (GPO) was the state postal system and telecommunications carrier of the United Kingdom until 1969. Before the Acts of Union 1707, it was the postal system of the Kingdom of England, established by Charles II in 1660. ...
specified CW1293 and CW1308 cables. CW1308 was a similar specification to the earlier CW1293 but with an improved color code. CW1293 used mostly solid colors on the cores making it difficult to identify the pair it was twisted with without stripping back a large amount of sheath. To solve this problem. CW1308 has narrow rings of the paired color printed over the base color. Both cables are a similar standard to category 3 cable.
Prior to the common use of polyethylene and other plastics for insulation, telephone twisted pair cable was insulated with waxed paper or cotton with a wax coating applied to the copper. The overall sheath of this type of cable was usually lead. This style of cable came into use in the late 19th century shortly after the invention of the telephone. The cable termination in termination boxes were sealed with molten wax or a resin to prevent the ingress of moisture which would seriously degrade the insulating properties of the paper insulation. However, such seals made future maintenance and changes more difficult. These cables are no longer made but are still occasionally encountered in old buildings and in various external areas, commonly rural villages.
Building infrastructure
Loaded
A loaded twisted pair has intentionally added inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...
and was formerly common practice on telecommunication lines. The added inductors are known as load coil
A loading coil or load coil is an inductor that is inserted into an electronic circuit to increase its inductance. The term originated in the 19th century for inductors used to prevent signal distortion in long-distance telegraph transmission c ...
s and reduce attenuation for voiceband
A voice frequency (VF) or voice band is the range of audio frequencies used for the transmission of speech.
Frequency band
In telephony, the usable voice frequency band ranges from approximately 300 to 3400 Hz. It is for this reason that ...
frequencies but increase it on higher frequencies. Load coils reduce distortion in voiceband on very long lines. In this context a line without load coils is referred to as an unloaded line.
Bonded
A bonded twisted pair is a construction variant in which the two wires of each pair are bonded together for the length of the cable. Pioneered by Belden, it is intended to help assure configuration consistency during and after installation. One key benefit is that the noise immunity performance of the cable can be protected despite potentially rough handling. The enhanced performance may be unnecessary and bonding reduces the flexibility of the cable and makes it prone to failure where it is flexed.
Twisted ribbon cable
A twisted ribbon cable is a variant of standard ribbon cable
A ribbon cable (also known as multi-wire planar cable) is a cable with many conducting wires running parallel to each other on the same flat plane. As a result, the cable is wide and flat. Its name comes from its resemblance to a piece of ribb ...
in which adjacent pairs of conductors are bonded and twisted together. The twisted pairs are then lightly bonded to each other in a ribbon format. Periodically along the ribbon, there are short sections with no twisting where connectors may be attached using the usual ribbon cable IDC techniques.
Solid-core vs. stranded cable
A solid-core cable uses one solid wire per conductor and in a four-pair cable there would be a total of eight solid wires. Stranded cable uses multiple wires wrapped around each other in each conductor and in a four-pair with seven strands per conductor cable, there would be a total of 56 wires (2 per pair × 4 pairs × 7 strands).
Solid core cable is intended for permanently installed runs (permanent link
A permalink or permanent link is a Uniform Resource Locator, URL that is intended to remain unchanged for many years into the future, yielding a hyperlink that is less susceptible to link rot. Permalinks are often rendered simply, that is, as cle ...
). It is less flexible than stranded cable and is more prone to failure if repeatedly flexed due to work hardening
In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context.
This strengt ...
. Stranded cable is used at patch panel
A patch panel is a device or unit featuring a number of jacks, usually of the same or similar type, for the use of connecting and routing circuits for monitoring, interconnecting, and testing circuits in a convenient, flexible manner. Patch ...
s and for connections from wall-ports to end devices (patch cord
A patch cable, patch cord or patch lead is an electrical or optical cable used to connect ("patch in") one electronic or optical device to another for signal routing. Devices of different types (e.g., a switch connected to a computer, or a sw ...
or drop cable), as it resists cracking of the conductors.
Connectors are designed differently for solid core than for stranded. Use of a connector with the wrong cable type can lead to unreliable cabling. Plugs designed for solid and stranded core are readily available, and some vendors even offer plugs designed for use with both types. The punch-down block
A punch-down block (also punchdown block, punch block, punchblock, quick-connect block and other variations) is a type of electrical connection often used in telephony. It is named because the solid copper wires are "punched down" into short open ...
s on patch-panel and wall-port jacks are designed for use with solid core cable. These work via the insulation-displacement method, whereby the device pierces the sides of the insulation and "bites" into the copper conductor to form a connection. Punchdown blocks are used as patch panels or as breakout boxes, for twisted pair cable.
Properties
Twisted pair has the following useful attributes:
* Electrical noise going into or coming from the cable can be prevented.
* Crosstalk
In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...
is minimized.
* Cheapest form of cable available for networking purposes.
* Easy to handle and install.
Twisted pair has the following limitations:
* Deformation: twisted pair's susceptibility to electromagnetic interference greatly depends on the pair twisting schemes 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 fragility of twisted-pair cables makes the installation practices an important part of ensuring the cable's performance.
* Delay skew: due to different twist rates used to minimize crosstalk between the pairs, different pairs within the cable have different lengths and thus different delays. This can degrade image quality when multiple pairs are used to carry components of a video signal. Low skew cable is available to mitigate this problem.
* Imbalance: differences between the two wires in a pair can cause coupling between the common mode and the differential mode. Differential to common mode conversion produces common-mode currents that can cause external interference and can produce common-mode signals in other pairs. Common mode to differential mode conversion can produce differential mode signals from common-mode interference from other pairs or external sources. Imbalance can be caused by asymmetry between the two conductors of the pair from each other and in relationship to other wires and the shield. Some sources of asymmetry are differences in conductor diameter and insulation thickness.
See also
* ANSI/TIA-568
ANSI/TIA-568 is a technical standard for commercial building cabling for telecommunications products and services. The title of the standard is ''Commercial Building Telecommunications Cabling Standard'' and is published by the Telecommunications I ...
* Balanced line
In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other ...
* Copper wire and cable
Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor.
Copper is the electri ...
* Ethernet over twisted pair
Ethernet over twisted-pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. They are a subset of all Ethernet physical layers.
Early Ethernet used various grades of coaxial cable, but in 1984, Sta ...
* Litz wire
Litz wire is a particular type of multistrand wire or cable used in electronics to carry alternating current (AC) at radio frequencies. The wire is designed to reduce the skin effect and proximity effect losses in conductors used at frequencies ...
* Registered jack
A registered jack (RJ) is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. Registration interfaces were first defined in the ...
, often used as connectors for twisted pair
* Star quad cable
Star-quad cable is a four-conductor cable that has a special quadrupole geometry which provides magnetic immunity when used in a balanced line. Four conductors are used to carry the two legs of the balanced line. All four conductors must be an ...
increases cancellation of interference
* Tip and ring
Tip and ring are the two conductors or sides of a telephone line. Their names are derived from the telephone plugs used for connecting telephone calls in manual switchboards. One side of the line is connected to the metal ''tip'' of the plug, and ...
Notes
References
External links
{{UTP Cable Standards
Communication circuits
Electromagnetic compatibility
Signal cables
Video hardware
2 (number)
19th-century inventions