Which device did Thomas Edison demonstrate at the 1876 Centennial Exhibition?

Thomas Edison demonstrated an automatic telegraph at the 1876 Centennial Exhibition.

The exhibition in Philadelphia marked the centennial of the United States Declaration of Independence and brought inventors, scientists, and manufacturers together. Edison displayed telegraph technology there, helping establish his public reputation before the phonograph and electric-lighting breakthroughs made him internationally famous.

Edison’s automatic telegraph was designed to transmit messages without requiring a human operator to handle every signal manually. His earlier work in telegraphy had provided both his technical foundation and his first business opportunities.

The exhibition is sometimes remembered chiefly for Alexander Graham Bell’s telephone demonstration. That event and Edison’s telegraph display occurred at the same major celebration, but they were different technologies and separate accomplishments.