This Month in Physics History

March 10, 1876: The First Transmission of Speech

Alexander Graham Bell

Contrary to popular belief, Alexander Graham Bell did not set out to construct the world's first telephone. Instead, his focus was on the development of the cutting edge technology of his day: the multiple telegraph, a device capable of sending multiple messages simultaneously over the same wire that was also the focus of his primary competitors, Thomas Edison and Elisha Gray.

A pivotal experiment on June 2, 1875 yielded a serendipitous discovery that changed the course of his research. Bell and his assistant, Watson, set up three multiple telegraph stations (A, B and C), each with three tuned-reed relays, to determine whether plucking the first reed in A would cause the corresponding reeds in B and C to vibrate. But while the corresponding reed in B vibrated well in response to A, the reed in C was stuck. When Watson plucked the reed, it produced multiple tones that caused the corresponding reed in B to vibrate powerfully - effectively demonstrating that a single reed, when dampened or stuck, could induce a current sufficient to transmit complex sounds over a distance.

Bell promptly constructed a prototype telephone in which the reed relay was attached to a membrane with a speaking cavity positioned above it, but this did not produce intelligible speech, apart from a low mumbling. Nevertheless, it was enough to convince Bell he was on the right track, and he submitted a patent for the device on February 14, 1876 - barely edging out Gray, who submitted his own design for a speaking telegraph a mere few hours later.

One month later, Bell once again revised his design. This new version included a speaking tube and membrane using a cork to attach a needle as a vibrating contact. One of his reed receivers was placed in another room, and Bell then spoke the now famous words - "Watson, come here; I want to see you." - to achieve the first documented transmission of human speech.

For a detailed discussion of Bell's work see www3.iath.virginia.edu/albell.

Birthdays for March:
March 4 — Robert R. Wilson (1914)
March 14 — Albert Einstein (1879)
March 22 — Robert A. Millikan (1868)
March 27 — Wilhelm Roentgen (1845)

Requiescat in Pace:
On March 31, 1727 Sir Isaac Newton, the "father of physics," dies in London, England