FOR THE PAST several years there have been three separate AIEE Standards bearing on the lightning Protective devices field: Report on Proposed Standard for Protector Tubes, AIEE 24, July 1940; American Standards for Lightning Arresters for A-C Power Circuits, AIEE 28, May 1944; and Proposed Standard for Expulsion Type Distribution Lightning Arresters, AIEE 47, December 1945; all prepared under the sponsorship of the AIEE Protective Devices Committee. By the time of the publication of AIEE Standard 47, it was evident that there was much material in these various Standards which had a common application, and many of the definitions and test procedures were common. W. J. Rudge, then Chairman of the Lightning Protective Devices Subcommittee of the Protective Devices Committee, perceived the advantages of merging all three Standards, and set up a working group for such a project.∗ It was believed that the combining of Standards on lightning protective devices not only should lead to improved nomenclature, but would bring into sharper focus the inherent characteristics of the different species of lightning arresters, and at the same time would improve the accessibility of desirable information.