These documents cover the years 1877-1880. Included are notes and drawings by Edison from March-September 1877 relating to patent models to be constructed by George M. Phelps. They are labeled "acoustic quadruplex," "sextuplex," "speaking telegraph," and "speaking telephone." Also included are four stencil pages, signed by George M. Phelps, Jr., containing notes and drawings of connections for a universal telephone desk set. The last item is a page from an 1880 pamphlet published by the American Bell Telephone Co. describing a universal desk set based on Edison's carbon transmitter.

Courtesy of the AT&T Archives and History Center.