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. Related material can be found in the Primary Printed Series and in Letterbooks, LM-012 and LM-013 (Letterbook Series).

All of the documents have been selected except for routine notices for meetings of the board of directors.