Techniques for the diagnosis of switching circuit failures

In 2.12 minutes, an IBM 7090 program found four input tests (for an 8-input parity check circuit) whose outcome determines whether any one of 102 possible failures occurred. For any single-output combinational circuit, with no more than 35 input variables, the program computes the set of all inputs detecting a given failure — the essential novelty of the method. These sets, one for each failure, are then processed to find a small subset of tests which detect any failure. The underlying method extends to the diagnosis of circuits with feedback.