Bypass Switching for Cellular Cascades

Faults can be circumvented in one-dimensional cellular arrays simply by switching out (bypassing) the defective cells in the cascade. In this note, the problem is solved of finding the minimal network of switches capable of bypassing up to q possibly defective cells from an n-celled array. The cells may be combinational or sequential, unilateral or bilateral, and may employ digital or continuous signals. It is shown that the minimum number N(n, q) of switches required equals ½(q+1)(2n-q+2) for the case when added internal circuit nodes are disallowed, or when q=1, and equals 3n otherwise.