This folder contains correspondence and other documents relating to the development and marketing of Edison's phonoplex and other systems of railway telegraphy. Included is information about the business of the Railway Telegraph & Telephone Co. and about the role of Alfred O. Tate as principal assistant for the phonoplex system. There is also some material pertaining to quadruplex telegraphy and to the manufacture of telegraph instruments.

All of the documents have been selected except for duplicate copies of selected documents.