This standard describes the independence requirements of the circuits and equipment comprising or associated with Class 1E systems@ including those required for safe shutdown. 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 This standard established the criteria for implementation of the independence requirements of IEEE Std 603-1980@ [12]1 ; ANSI/ IEEE Std 279-1971 [3]; IEEE Std 308-1980 [9].In addition@ this standard provides interim criteria for implementation of independence requirements for safe shutdown systems. 1The numbers in brackets correspond to the references listed in Section 4 of this standard.