Phones

First telphone invention

May 5, 1876

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Telephone transmission extends across and between major cities

May 5, 1900

As telephone transmission extends across and between major cities, "loading coils" or inductors are placed along the lines to reduce distortion and attenuation or the loss of a signal's power.
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Fleming invents the vacuum diode

Sep 5, 1904

British engineer Sir John Ambrose Fleming invents the two-electrode radio rectifier; or vacuum diode, which he calls an oscillation valve
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First transcontinental telephone call

Dec 14, 1915

Alexander Graham Bell makes the first transcontinental telephone call to Thomas Watson-from New York to San Francisco-after trials using De Forest’s triodes successfully boost the long-distance signal.
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Switching systems and rotary-dial telephones

Mar 2, 1919

Bell System companies begin installing switching systems and rotary-dial telephones, though dial phones have been around since just before the turn of the century.
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Frequency multiplexing concept

May 11, 1920

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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North American Numbering Plan

Jan 6, 1947

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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A Mathematical Theory of Communication

Nov 15, 1948

Bell Labs’s Claude Shannon publishes the landmark paper "A Mathematical Theory of Communication," which provides mathematicians and engineers with the foundation of information theory.
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First phone to combine a ringer and handset

Dec 4, 1949

AT&T introduces the Model 500 telephone, the first that combines a ringer and handset. The classic black rotary phone, featuring an adjustable volume control for the bell and later a variety of colors, becomes a cultural icon.
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Direct longdistance calling first available

Oct 16, 1951

In a test in Englewood, New Jersey, customers are able to make long-distance calls within the United States directly, without the assistance of an operator. But it takes another decade for direct long-distance dialing to be available nationwide.
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