09/10/1892 Pennsylvania Railroad and Ettinger, William to Edison, Thomas Alva
(Logue, William S; Fondersmith, Harry) Phonoplex and railroad telegraphy [Attachment/Enclosure]
[D9247]  Document File Series -- 1892: (D-92-47) Telegraph -- Phonoplex
[D9247AAC; TAEM 133:749]
Courtesy of Thomas Edison National Historical Park.