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A ‐out‐of‐ (oo) voted structure is functioning as long as at least of its blocks are functioning (). Observe that an oo voted structure is a series structure and a 1oo structure is a parallel structure.

A 2oo3 voted structure is shown in Figure 2.14. Two different diagrams are shown. The diagram to the left is a physical diagram that shows the 2oo3 logic, whereas the RBD to the right is a series–parallel structure. In the RBD, we see that the system is functioning when block 1 AND block 2 are functioning OR block 1 AND block 3 are functioning OR block 2 AND block 3 are functioning. Observe that each block appears in two different places in this RBD. This shows that an RBD is not a physical layout diagram, but a logical graph illustrating the specified function of the system.

Figure 2.14 Voted structure 2oo3, (left) a physical diagram and (right) an RBD.