This collection consists primarily of letters exchanged between Edison and Secretary of the Navy Josephus Daniels, along with related correspondence. Many of the typewritten letters are accompanied by drafts in Edison's hand. The documents in this folder cover the periods February-March 1917 and December 1918-February1919. They pertain to Edison's experiments on a phonographic range finder (also known as an audible range finder) that would detect the position of enemy guns by their sound. The correspondents include Edison employee Newman Henry Holland, who conducted experiments with the range finder at the Sandy Hook Proving Ground in December 1918; Maj. Gen. Henry Jervey of the U.S. War Dept.; and Maj. Gen. William Murray Black of the U.S. Corps of Engineers. Several photographs of the invention are included with the reports, along with a typewritten memorandum explaining how the invention worked and a drawing by Holland showing the position of the three receiving horns at Sandy Hook in relation to the gun. Daniels's letter of March 26 discusses several projects in addition to the range finder, and extracts from this letter can be found in Reports 10, 12, 15, 17, and 18; Reports 17 and 18 also contain extracts from Edison's response of March 28. Additional material about the range finder can be found in Report 13 and in Direction Finder (1917), Naval Consulting Board and Wartime Research Papers. Correspondence regarding a related invention, the Aeroplane Detector, can be found in Report 39.

This project is described on pp. 187-189 of Lloyd N. Scott's Naval Consulting Board of the United States.