This folder contains correspondence and other documents pertaining to the Edison Phonoplex System of Telegraphy. Most of the documents relate to the installation of phonoplex circuits on various American and Canadian railroads. Some of the items deal with the problem of finding suitable batteries, condensers, and other components. Much of the correspondence is by W.S. Logue, field agent for the phonoplex system. Most of Logue's letters are addressed to Edison's secretary, Alfred O. Tate. Tate served as the company's electrician and oversaw its daily business operations. Edison himself was only tangentially involved in phonoplex operations, and very few letters to or from him can be found in this folder.

Less than 10 percent of the documents have been selected. The case study approach begun in 1887 continues for the Pennsylvania Railroad. Substantive items relating to the operation of the phonoplex on that railroad have been selected, as well as one letter from Edison to Albert B. Chandler, president and general manager of the Postal Telegraph Cable Co., soliciting phonoplex business.

The following categories of documents have not been selected: most documents dealing with phonoplex operations on other railroads; routine correspondence with the Edison Manufacturing Co. regarding manufacture of the Edison-Lalande battery; routine inquiries from railroad companies; Logue's accounts and personal correspondence, including lengthy letters about his health.

Related documents can be found in D-92-20 (Edison Manufacturing Co. - General).