The dual-numbered designation of the fast transient test is a detail that causes avoidable difficulty in European conformity work, and understanding it saves time. CENELEC publishes such a document when it adopts an International Electrotechnical Commission text without technical change: the resulting standard carries both numbers, its foreword states that the international publication has been adopted unmodified, and an annex relates it to the directive concerned. Consequently the dual-numbered edition, the plain European edition and the international standard all describe the same test, with the same waveform, the same coupling networks and the same levels, and a test report issued against one is technically equivalent to a report issued against another. The practical point is one of citation: the declaration of conformity should name the edition that is currently listed for the directive, and the dual number is the way that edition is identified.