22.2 MB (1.1 MB compressed)
2724 x 2849 pixels
23.1 x 24.1 cm ⏐ 9.1 x 9.5 in (300dpi)
SCIENCE SOURCE / SCIENCE PHOTO LIBRARY SCIENCE SOURCE / SCIENCE PHOTO LIBRARY
A 19th century illustration of the proper use of a Bell telephone, where the microphone and speaker are separate devices. A telephone converts sound, typically and most efficiently the human voice, into electronic signals suitable for transmission via cables or other transmission media over long distances, and replays such signals simultaneously in audible form to its user. In 1876, Scottish-American Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice. This instrument was further developed by many others.
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