Redundancy
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Redundancy
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1. In information theory: of a source, the amount by which the logarithm
of the number of symbols available at the source exceeds the average information
content per symbol of the source.
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The term redundancy has been used loosely in other senses. For example,
a source whose output is normally transmitted over a given channel has been
called redundant, if the channel utilization index is less than unity.
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2. The existence of more than one means for accomplishing a given task,
where all means must fail before there is an overall failure to the system.
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Parallel redundancy applies to systems where both means are working at
the same time to accomplish the task, and either of the system is capable
of handling the job itself in case of failure of the other system. Standby
redundancy applies to a system where there is an alternative means of accomplishing
the task that is switched in by a malfunction sensing device when the primary
system fails. [[/a>|/a>
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
