05/16/1877 Edison, Thomas Alva -- Technical Notes and Drawings
(Phelps, George May, Jr; Prescott, George Bartlett) Telephone; Acoustic telegraphy
[X012L2]  AT&T Archives and History Center, Warren, N.J.: Western Electric Manufacturing Company Records -- Technical Notes and Drawings (Box 92)
[X012L2B; TAEM 0:0]
Courtesy of the AT&T Archives and History Center.