This undated notebook was probably used during the period December 1911-January 1912. The entries, which are all by Edison, consist primarily of drawings and calculations relating to phonographs and cylinder phonograph records. Included are drawings of cabinet phonographs with internal horns, machines used to manufacture records, and various recorders and tone arm arrangements, along with rough calculations on the expense, labor, chemicals, and pace of record production. Other entries pertain to storage batteries or consist of calculations and partial sketches with little or no identifying context. Also included is a partial draft of a February 1912 agreement involving the Edison Storage Battery Co., Hartford Electric Light Co., and General Vehicle Co. The inside front cover and first page contain inscriptions by Edison's youngest son, Theodore. The pages are unnumbered, and several have been removed from the front and the center of the book. Approximately 135 pages have been used. Courtesy of Thomas Edison National Historical Park.