A multiplex system, a system equivalent to a series ofnstructures ofmparallel elements which is sometimes called component redundancy, is studied and found to be superior to a parallel system consisting ofmparallel redundant structures ofnunits which is sometimes called unit redundancy. A guideline for the reduction of the probability of parallel system failure by the multiplex system whenn≤10,m≤4 is 1/nm-1ifƛt<.1 whereƛis the constant failure rate andtis the time of system operation. Additional isolation components and less than complete multiplexing (combination of multiplexing and parallel system) may offer reliability improvement in design when the physical act of complete multiplexing is prohibitive.