This letterbook covers the period July 1890-October 1892. Most of the letters are by Edison's secretary, Alfred O. Tate, who served as electrician and business manager. A few of the letters are by Edison; there is also correspondence by Thomas Maguire, secretary, and W. S. Logue, field agent. The letters deal mainly with the sale, installation, and operation of the phonoplex system in the United States and Canada. There are also general inquiries about the system and material relating to contracts. The recipients include Charles D. Shain of the Edison General Electric Co. and various railroad company officials. A few letters signed by Tate as Edison's private secretary do not concern the phonoplex; these are similar in character to those found in the General Letterbooks. The front cover is labeled "Phonoplex Book Only." The spine is stamped "1890-1892 Phonoplex." The book contains 501 numbered pages and an index (not selected). Less than 10 percent of the book has been selected.