[A] key held for use under specific operational conditions or in support of specific contingency plans. [INFOSEC-99]

1. A plan for backup procedures, emergency response, and post-disaster recovery. Synonym disaster recovery plan. [2382-pt.8]
2. [A] plan maintained for emergency response, backup operations, and post-disaster recovery for an information system (IS), to ensure the availability of critical resources and to facilitate the continuity of operations in an emergency situation. [INFOSEC-99]

A procedure that is an alternative to the normal path of a process if an unusual but anticipated situation occurs. [2382-pt.8]

A check made of a circuit to verify that a communication or power path exists.

A device that is used to interconnect the Go and Return paths of a circuit at the incoming end, and through which the detection of an incoming check tone transmits another check tone to permit a continuity checking of a 2-wire circuit. [After T1.110-1987] Synonym [loosely] smart jack.

1. Operation in which certain components, such as nodes, facilities, circuits, or equipment, are in an operational state at all times.
Note: Continuous operation usually requires that there be fully redundant configuration, or at least a sufficient X out of Y degree of redundancy for compatible equipment, where X is the number of spare components and Y is the number… (Read More →)

In teleconferencing, the concurrent presence of two or more video images, such as two images that may appear on a single monitor on a split screen or on two separate monitors.

A characteristic of an image (e.g., a photograph) such that the image has all the values (0 to 100%) of gray (black and white) or color in it.
Note: A continuous tone can be approximated by the use of thousands or millions of gradations of black and white or colors. The granularity of computer screens (viz. , pixel size) can… (Read More →)

In facsimile, an object, i.e., an original, or a recorded copy, that contains shades of gray, i.e., contains densities between black and white, such as in a photographic print.

A wave of constant amplitude and constant frequency.