Unbound Notebooks, Vol. 15 (1875-1877)
This volume contains only a few dated entries, covering the years 1875-1877. The notes and drawings are by Edison, Charles Batchelor, and James Adams. They relate to acoustic and multiple telegraphy, the speaking telegraph and telephone, the phonograph recorder, and the etheroscope. The volume consists of 174 numbered, unbound pages.
Missing pages: 1, 3, 5, 7-8, 37, 41, 44-45, 169. Other pages missing from this volume can be found in facsimile in the Telephone Interferences."