Balanced line

balancedbalanced pairbalanced circuitbalanced differential signalingbalanced linesbalanced mono signalbalanced outputbalanced signalbalanced signal linesbalanced signal pair
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits.wikipedia
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Twisted pair

twisted-pairunshielded twisted pairshielded twisted pair
Common forms of balanced line are twin-lead, used for radio frequency signals and twisted pair, used for lower frequencies.
Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighboring pairs and improves rejection of external electromagnetic interference.

Balanced circuit

balancedbalancebalanced ports
Balanced and unbalanced circuits can be interconnected using a transformer called a balun.
A balanced circuit is circuitry for use with a balanced line or the balanced line itself.

Unbalanced line

unbalancedunbalanced signalingunbalanced transmission line
They are to be contrasted to unbalanced lines, such as coaxial cable, which is designed to have its return conductor connected to ground, or circuits whose return conductor actually is ground.
In electrical engineering, an unbalanced line is a transmission line, often coaxial cable, whose conductors have unequal impedances with respect to ground; as opposed to a balanced line.

Balun

matching transformerchoke balunmatched
Balanced and unbalanced circuits can be interconnected using a transformer called a balun.
A balun (for balanced to unbalanced) is an electrical device that converts between a balanced signal and an unbalanced signal.

Repeating coil

transformer
This may be achieved by transformer coupling or by merely balancing the impedance in each conductor.
In telecommunications, a repeating coil is a voice-frequency transformer characterized by a closed magnetic core, a pair of identical balanced primary (line) windings, a pair of identical but not necessarily balanced secondary (drop) windings, and low transmission loss at voice frequencies.

Star quad cable

star-quad cable
Some balanced lines use 4-conductor star quad cable to provide immunity to magnetic fields.
Star-quad cable is a four conductor cable that has a special quadrupole geometry that provides magnetic immunity when used in a balanced line.

Loading coil

load coilloaded cableloading coils
Loading coils were used to improve the distance achievable with cable but the problem was not finally overcome until amplifiers started to be installed in 1912.
Submarine communications cables are particularly subject to the problem, but early 20th century installations using balanced pairs were often continuously loaded with iron wire or tape rather than discretely with loading coils, which avoided the sealing problem.

Category 5 cable

CAT5Category 5Cat 5e
Examples of twisted pairs include category 5 cable.
Most Category 5 cables are unshielded, relying on the balanced line twisted pair design and differential signaling for noise rejection.

Transmission line

transmission linestransmissionbalanced transmission line
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits.
Other times it is used for a single, balanced line, such as audio applications and 2-wire telephony.

Transformer

power transformerelectrical transformerprimary winding
Balanced and unbalanced circuits can be interconnected using a transformer called a balun.
A balun transformer converts a signal that is referenced to ground to a signal that has balanced voltages to ground, such as between external cables and internal circuits.

Twin-lead

ladder linetwin leadOpen-wire "Ladder" Line
Common forms of balanced line are twin-lead, used for radio frequency signals and twisted pair, used for lower frequencies.
Twin-lead cable is a two-conductor flat cable used as a balanced transmission line to carry radio frequency (RF) signals.

Unbalanced circuit

unbalanced
Balanced and unbalanced circuits can be interconnected using a transformer called a balun.
For this reason, balanced lines are normally driven from balanced circuits.

Mixing console

mixermixing deskmixing board
Providing that the receiving end (usually a mixing console) does not disturb the line balance, and is able to ignore common-mode (noise) signals, and can extract differential ones, then the system will have excellent immunity to induced interference.
Balanced inputs and connectors, such as XLR or phone connectors, reduce interference problems.

Coaxial cable

coaxialcoax cablecable
They are to be contrasted to unbalanced lines, such as coaxial cable, which is designed to have its return conductor connected to ground, or circuits whose return conductor actually is ground.
Balanced line

Common-mode interference

common-mode noisecommon mode currentcommon mode signal
Any external signal sources tend to induce only a common mode signal on the line, and the balanced impedances to ground minimizes differential pickup due to stray electric fields.
A signal transformer may have a center tapped primary to ground, with the signal and signal return operating as a balanced line (push-pull technique). This is advantageous; its resistance to signals raised on ground due to ground loop induction and ground circuit resistance.

Frequency-division multiplexing

frequency division multiplexingFDMfrequency division multiplex
Telephone trunk lines, and especially frequency division multiplexing carrier systems, are usually 4-wire circuits rather than 2-wire circuits (or at least they were before fibre-optic became widespread) and require a different kind of cable.
For shorter distances, cheaper balanced pair cables were used for various systems including Bell System K- and N-Carrier.

RS-485

EIA-485RS485Serial
RS-485
Electrical signaling is balanced, and multipoint systems are supported.

Differential signaling

differentialdifferential pairdifferential signals
Lines carrying symmetric signals (those with equal but opposite voltages to ground on each leg) are often incorrectly referred to as "balanced", but this is actually differential signaling.
This advantage is not directly due to differential signaling itself, but to the common practice of transmitting differential signals on balanced lines.

Telecommunication

telecommunicationscommunicationstelecom
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits.

Professional audio

pro audioprofessionalaudio professionals
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits.

Electrical impedance

impedanceimpedancescomplex impedance
In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits. Any external signal sources tend to induce only a common mode signal on the line, and the balanced impedances to ground minimizes differential pickup due to stray electric fields.

Ground (electricity)

groundgroundinggrounded
They are to be contrasted to unbalanced lines, such as coaxial cable, which is designed to have its return conductor connected to ground, or circuits whose return conductor actually is ground. In telecommunications and professional audio, a balanced line or balanced signal pair is a transmission line consisting of two conductors of the same type, each of which have equal impedances along their lengths and equal impedances to ground and to other circuits.

Differential amplifier

long-tailed pairdifferentiallong-tailed
The chief advantage of the balanced line format is good rejection of external noise when fed to a differential amplifier.

Faraday's law of induction

Faraday's lawinductionelectromagnetic induction
Any external signal sources tend to induce only a common mode signal on the line, and the balanced impedances to ground minimizes differential pickup due to stray electric fields.

Faraday cage

electrostatic shieldingFaraday shieldFaraday shields
Some balanced lines also have electrostatic shielding to reduce the amount of noise introduced.