1. In the transmission of data, the excess of transmitted message symbols over that required to convey the essential information in a noise-free circuit.
Note: Redundancy may be introduced intentionally (as in the case of error detection or correction codes) or inadvertently (such as by oversampling a band-limited signal, inefficient formats, etc. ).
2. In a communication system, surplus capability… (Read More →)

1. A method of verifying that any redundant hardware or software in a communication system is in an operational condition.
2. A check that uses one or more extra binary digits or characters attached to data for the detection of errors.

A code using more signal elements than necessary to represent the intrinsic information.
Note: The redundancy may be used for error-control purposes.

An antenna that may be real, virtual, or theoretical, and has a radiation pattern that can be used as a basis of comparison with other antenna radiation patterns.
Note: Examples of reference antennas are unit dipoles, half-wave dipoles, and isotropic, i.e., omnidirectional antennas. [From Weik '89]

[In television,] The level corresponding to the specified maximum excursion of the luminance signal in the black direction. [47CFR]

A hypothetical circuit of specified equivalent length and configuration, and having a defined transmission characteristic or characteristics, used primarily as a reference for measuring the performance of other, i.e., real, circuits or as a guide for planning and engineering of circuits and networks.
Note: Normally, several types of reference circuits are defined, with different configurations, because communications are required over… (Read More →)

1. A clock with which another clock is compared.
2. A clock, usually of high stability and accuracy, used to govern a network of mutually synchronized clocks of lower stability.
Note: The failure of a reference clock does not necessarily cause loss of synchronism.

The geometric representation of colors in three-dimensional space. [CIE 845-03-25]
Note: There are three reference spaces recognized by ISO 8613: CMYK color space; CIELuv color space, and R,G,B color space. [After SMPTE]

In ISDN, a combination and arrangement of functional groups and reference points that reflect possible network topology.

an information transfer between two server application processes acting cooperatively on instructions from a third application process.