[QCC01136], Legal Testimony, William Orton, May 17th, 1877
Multiple telegraphy (duplex, quadruplex)
[QCC01-F] Litigation Series -- Quadruplex Case, Volume 71
https://edisondigital.rutgers.edu/document/QCC01136
Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
Archive.org Viewer, Microfilm Series Reel 10