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. Other letters concern the suitability of the phonoplex for Europe. 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.

Approximately 20 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. The case study of the Chicago and Grand Trunk has been discontinued, as the character of the documents becomes routine following the installation of the system in 1887. The following categories of documents have also been selected: documents indicating Edison's own involvement with the phonoplex; items relating to foreign phonoplex operations; and one letter from Charles Selden of the Baltimore and Ohio Telegraph Co. regarding a special discount for his company's use of the phonoplex.

The following categories of documents have not been selected: most documents dealing with phonoplex operations on other railroads; correspondence regarding problems with phonoplex instruments supplied by Bergmann and Co.; letters concerning the manufacture of sample equipment by the Edison Electric Light System of Canada in order to protect Edison's Canadian patent rights; routine inquiries from railroad companies; Logue's accounts and personal correspondence.

Related material can be found in D-88-01 (Battery) and D-88-02 (Bergmann & Co.).