EDISON SELLS HIS TELEGRAPH PATENT
EDISON, THOMAS ALVA. 1847-1931. Manuscript Document Signed on vellum ('Thomas Alva Edison') being the agreement between Edison and William Orton, president of Western Union, selling the British rights to Edison's telegraph patent just days after testing his new invention the telephone, folio (380 x 256 mm), 2 pp, on first leaf of a bifolium, New York, January 12, 1878, docket to verso of second leaf 'Assignment of entire right in British Letters Patent No 384 ... for Duplex and Multiplex Telegraphs,' British stamps affixed to both written pages, with certification of Her Brittanic Majesty's Consulate General, New York, with wax seal, attached with string, minor wear, minor soiling to vellum.

SIGNED CONTRACT FOR THE SALE OF EDISON'S TELEGRAPH PATENT IN THE UK, FOLLOWING CLOSELY ON THE HEELS OF HIS 'SPEAKING TELEGRAPH' (OR TELEPHONE). The end of 1877 and beginning of 1878 was a busy time for Edison, beginning with his invention of the carbon button transmitter, which greatly improved upon Bell's telephone. Working with Western Union, Edison devised a system by which a small piece of carbon was placed beneath the diaphragm, so that when the voice vibrated the diaphragm the vibration of the button changed, varying the current. By February 1878, he had finalized the form and the design, and Western Union began production out of Menlo Park. Edison's basic transmitter design would remain in use until the advent of digital telephone systems, and would have a profound impact on the broadcast and recording industries as well.