1947 North American Numbering Plan 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. The first three digits of a typical number identify the area being called; the next three, called the prefix, locate the closest central or switching office; and the last four digits represent the line number. Bell Labs conceives the idea of reusing radio frequencies among hexagonal "cells"—the beginning of the drive toward cellular communications. Mobile phones become an even more realistic dream with the invention of the transistor, which eventually makes them possible.
1948 A Mathematical Theory of Communication 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. The paper seeks to answer questions about how quickly and reliably information can be transmitted. 1948 A Mathematical Theory of Communication 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. The paper seeks to answer questions about how quickly and reliably information can be transmitted. 1949 First phone to combine a ringer and handset 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. 1951 Direct longdistance calling first available 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. 1956 First transatlantic telephone cable The first transatlantic telephone cable—the TAT-1—is installed from Scotland to Nova Scotia, providing telephone service between North America and the United Kingdom. Additional circuitry through London links Western European countries such as Germany, France, and the Netherlands. A joint project of the United States, Canada, and Britain, the TAT-1 takes 3 years and $42 million to plan and install, using 1,500 nautical miles of specially insulated coaxial cable. It handles up to 36 simultaneous calls and supplements existing telegraph and radiophone links. The first TAT-1 call is placed on September 25 by the U.K. postmaster to the chairman of AT&T and the Canadian Minister of Transport.
1962 First commercial digital transmission system Illinois Bell turns on the first commercial digital transmission system, known as the T1 (Transmission One), which eventually replaces analog lines. The multiplexed system carrying voice signals has a total capacity of 1.5 million bits (or binary digits) per second and is less susceptible to electrical interference from high-tension wires. The T1 quickly becomes the main transmission system for long-distance telephone service and, eventually, local calls. Bell Systems demonstrates the first paging system at the Seattle World’s Fair. Called Bellboy, the personal pager is one of the first consumer applications for the transistor. An audible signal alerts customers, who then call their offices or homes from a regular phone to retrieve their messages. 1962 First commercial digital transmission system Illinois Bell turns on the first commercial digital transmission system, known as the T1 (Transmission One), which eventually replaces analog lines. The multiplexed system carrying voice signals has a total capacity of 1.5 million bits (or binary digits) per second and is less susceptible to electrical interference from high-tension wires. The T1 quickly becomes the main transmission system for long-distance telephone service and, eventually, local calls. Bell Systems demonstrates the first paging system at the Seattle World’s Fair. Called Bellboy, the personal pager is one of the first consumer applications for the transistor. An audible signal alerts customers, who then call their offices or homes from a regular phone to retrieve their messages. 1962 Telstar 1 Communications satellite Telstar 1 is launched by a NASA Delta rocket on July 10, transmitting the first live transatlantic telecast as well as telephone and data signals. At a cost of $6 million provided by AT&T, Bell Telephone Laboratories designs and builds Telstar, a faceted sphere 34 inches in diameter and weighing 171 pounds. The first international television broadcasts shows images of the American flag flying over Andover, Maine to the sound of "The Star-Spangled Banner." Later that day AT&T chairman Fred Kappel makes the first long-distance telephone call via satellite to Vice President Lyndon Johnson. Telstar I remains in orbit for seven months, relaying live baseball games, images from the Seattle World's Fair, and a presidential news conference. 1963 Touch-tone telephone is introduced The touch-tone telephone is introduced, with the first commercial service available in Carnegie and Greensburg, Pennsylvania, for an extra charge. The Western Electric 1500 model features 10 push buttons that replace the standard rotary dial. A 12-button model featuring the * and # keys comes out soon afterward and replaces the 10-button model. 1965 First electronic central office switching system The first electronic central office switching system, the 1 ESS, is installed in Succasunna, New Jersey, after years of research and planning and at a cost of $500 million. Switching systems switch telephone traffic through local central offices that also house transmission equipment and other support systems. The 1 ESS has the capacity to store programs and allows such features as call forwarding and speed dialing. The 4 ESS, developed by Western Electric in 1976, is the first digital switch and will remain the workhorse system for several decades before increases in the transmission of data, as well as voice signals, spur new advances.
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