This paper is concerned with the detection of redundant leads in redundant logic networks. The concept of dynamic testing is introduced. We shall show that some traditionally caled undetectable faults may become detectable in dynamic testing, or how to make them become detectable in dynamic testing. Conditions for certain redundancies to be definitely untestable are also discussed.

A compatibility relationship on network paths is defined in such a way that the maximal compatibles are isomorphic to the products in the "structure and parity-observing output function" (SPOOF), a subscripted Boolean expression for the network output that uniquely specifies the network structure. For a given network, the path compatibility relations are easy to find, as are the maximal compatibles and hence the SPOOF for the network output. Because the collection of all the path compatibility relations, conveniently displayed in matrix form, completely characterizes the network, the compatibility matrix can be used for a variety of purposes.