Redundancy Definitions

Going through my notes on this, I have a lot of defintions with 
regards to redundancy and different schemes.  Here is the base 
definitions from some reasonable references.

- - - - - -

The existence of more than one means for accomplishing a given 
function.  Each means of accomplishing the function need not 
necessarily be identical [1].

REDUNDANCY: The existence of more than one means for accomplishing a 
given function.  Each means of accomplishing the function need not 
necessarily be identical. The two basic types of redundancy are 
active and standby. [2]

   Active Redundancy - Redundancy in which all redundant items
   operate simultaneously.

   Standby Redundancy - Redundancy in which some or all of the
   redundant items are not operating continuously but are
   activated only upon failure of the primary item performing
   the function(s).

[1] Reliability Engineering for Electronic Design, Norman B. Fuqua,
    Reliability Analysis Center, Griffis Air Force Base, 1987

[2] ELECTRONIC RELIABILITY DESIGN HANDBOOK, MIL-HDBK-338B, 1
    October 1998

-- 
rk, Just an OldEngineer
"In God we trust, all others bring data." 
-- Framed plaque from the '60s, hanging in the Mission Evaluation
   Room at Johnson Space Center, downstairs from Mission Control.