IEC 62808:2015+A1:2018 establishes requirements for the design, analysis and qualification of isolation devices used to ensure electrical independence of redundant safety system circuits, or between safety and lower class circuits, as specified in IEC 60709. This standard includes guidance on the determination of the maximum credible fault that is applied to the isolation devices. The maximum credible fault can be used as a basis for the test levels used in testing based on other standards (e.g. IEC TS 61000-6-5 or IEC 62003). This consolidated version consists of the first edition (2015) and its amendment 1 (2018). Therefore, no need to order amendment in addition to this publication.