The scope of this document is the independence requirements of the circuits and equipment comprising or associated with Class 1E systems. It sets forth criteria for the independence that can be achieved by physical separation and electrical isolation of circuits and equipment which are redundant but does not address the determination of what is to be considered redundant. Purpose The purpose of this document is to establish the criteria for implementation of the independence requirements of IEEE Std 279-1971. Criteria for Protection Systems for Nuclear Power Generating Stations (ANSI N42.7.1972)@ and IEEE Std 308-1974@ Criteria for Class 1E Power Systems for Nuclear Power Generating Stations.