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In 1753, one Scottish scientist named Charles Morrison proposed an important theory: you could transmit messages through electricity by using different wires for each letter.
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During the 1870's, two well known inventors both independently designed devices that could transmit sound along electrical cables.
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Alexander Graham Bell was awarded the first U.S. patent for the invention of the telephone in 1876.
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AT&T develops the frequency multiplexing concept, in which frequencies of speech are shifted electronically among various frequency bands to allow several telephone calls at the same time.
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In 1946, Swedish police used the first mobile phone.
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With the rapidly growing number of telephone customers, AT&T and Bell Labs develop the North American Numbering Plan, a system that assigns telephone numbers to customers in the United States and its territories as well as Canada and many Caribbean nations.
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AT&T introduces the Model 500 telephone, the first that combines a ringer and handset.
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The touch-tone telephone is introduced, with the first commercial service available in Carnegie and Greensburg, Pennsylvania, for an extra charge.
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By 1967, mobile phone technology allowed the user to stay within a very limited calling area.
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The number of cellular telephone subscribers in the United States grows to 100 million, from 25,000 in 1984.
