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12-01-2016

Alexander Graham Bell makes 1st sound transmission, June 2, 1875

Amy Norcross

EDN

In 1875, while working on a harmonic telegraph, Alexander Graham Bell and Thomas Watson made an important discovery by accident.

Bell had opened the School of Vocal Physiology and Mechanics of Speech for deaf students in Boston in 1872, where Helen Keller was one of his most famous students. He continued his research and experiments in sound while teaching vocal physiology and speech at Boston University.

Alexander Graham Bell makes 1st sound transmission, June 2, 1875

It was there that Bell and his assistant Watson discovered a way to transmit sound over a wire. Bell had been experimenting with electric signals with the intention to improve the telegraph, which had been an established means of communication for decades but was limited by its ability to send and receive only individual messages. Bell envisioned a time when multiple messages could be transmitted simultaneously and used a “harmonic telegraph” as the basis for his research. The principle behind the harmonic telegraph was that several notes could be sent along the same wire at the same time if each note, or message, was transmitted at a different pitch.

On June 2, 1875, while working in one room with their experimental telegraphic device, Watson tried to free a reed that had been too tightly wound around the pole of its electromagnet. He inadvertently plucked the reed, which produced a twang that Bell heard on a second device in another room. This discovery led Bell to change his focus from improving the telegraph to figuring out a way to realize the potential for voice transmissions. He and Watson spent the next several months creating a working transmitter that was capable of varying electronic currents and a receiver that would reproduce those variations in audible frequencies. On March 10, 1876, speaking through the instrument he developed, Bell called his assistant in the next room: “Mr. Watson, come here. I want to see you.”

Alexander Graham Bell makes 1st sound transmission, June 2, 1875
This is a handwritten transcript of an audio recording
(dated April 15, 1885) containing Alexander
Graham Bell’s voice.

The recording, contained on a wax-on-binder-board disc, was confirmed to be Bell’s voice and restored in 2013 by the Smithsonian Institution’s National Museum of American History, as part of a collaborative project with the Library of Congress and Lawrence Berkeley National Laboratory. Hear the recording in the video below.

On February 14, 1876, before his famous “call” to Watson, Bell applied for a patent for his improvements in telegraphy. At about the same time another inventor, Elisha Gray, also designed a device that could transmit speech electrically, but Bell is widely considered the inventor of the first practical telephone. On June 11, 2002, however, the United States Congress declared that honor should instead go to Italian immigrant Antonio Meucci.

Video

EDN

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