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Alexander Graham Bell's invention of the telephone in 1876 rang in the era of talking at a distance. Innovators in the 20th century expanded the telephone's reach across continents and oceans, figuratively shrinking the world and connecting its citizens. Electronic switching systems and other technological advances helped customers place calls without the help of operators. By the year 2000, more than a billion people all over the world had gone wireless—using cellular technology to talk and deliver text and photos on super-lightweight telephones smaller than a deck of cards.
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1900 |
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Telephone transmission extends across and between major cities
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. Independently invented by the American Telephone and Telegraph Company's (AT&T) George Campbell and Michael Pupin of Columbia University, the loading coils are first used commercially in New York and Boston, nearly doubling the transmission distance of open lines. Pupin is awarded the patent for the device in 1904, and AT&T pays him for its use.
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1904 |
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Fleming invents the vacuum diode
British engineer Sir John Ambrose Fleming invents the two-electrode radio rectifier; or vacuum diode, which he calls an oscillation valve. Based on Edison's lightbulbs, the valve reliably detects radio waves. Transcontinental telephone service becomes possible with Lee De Forest's 1907 patent of the triode, or three-element vacuum tube, which electronically amplifies signals.
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1915 |
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First transcontinental telephone call
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. What is the world’s longest telephone line consists of 2,500 tons of copper wire, 130,000 poles, three vacuum-tube repeaters, and countless numbers of loading coils.
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1919 |
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Switching systems and rotary-dial telephones
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. The dial makes it easier for customers to place calls without an operator. The finger wheel of the dial interrupts the current in the phone line, creating pulses that correspond to the digits of the number being called.
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1920 |
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Frequency multiplexing concept
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. Metal coaxial cable eventually is used to carry a wide range of frequencies.
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1947 |
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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.
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1948 |
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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.
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1949 |
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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.
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1951 |
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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.
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1956 |
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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.
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1962 |
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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.
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1962 |
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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.
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1963 |
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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.
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1965 |
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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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1968 |
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First 911 call is made
On February 16 the first 911 call is made in Haleyville, Alabama. Legislation calling for a single nationwide phone number for citizens to use to report fires and medical emergencies was passed by Congress in 1967, and in January 1968 AT&T announced plans to put such a system into place. An independent company, Alabama Telephone, scrambled to build its own system and succeeded in beating AT&T to the punch. The numbers 911 were chosen because they were easy to remember and did not include three digits already in use in a U.S. or Canadian area code. In Britain a national emergency number—999—had been in place since the late 1930s.
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1973 |
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First portable cell phone call is made
The first portable cell phone call is made by Martin Cooper of Motorola to his research rival at Bell Labs, Joel Engel. Although mobile phones had been used in cars since the mid-1940s, Cooper’s was the first one invented for truly portable use. He and his team are awarded a patent in 1975.
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1975 |
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U.S. military begins using fiber optics
The U.S. military begins using fiber optics to improve communications systems when the navy installs a fiber-optic telephone link on the USS Little Rock. Used to transmit data modulated into light waves, the specially designed bundles of transparent glass fibers are thinner and lighter than metal cables, have greater bandwidth, and can transmit data digitally while being less susceptible to interference. The first commercial applications come in 1977 when AT&T and GTE install fiber-optic telephone systems in Chicago and Boston. By 1988 and 1989, fiber-optic cables are carrying telephone calls across the Atlantic and Pacific Oceans.
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1976 |
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Common channel interoffice signaling
AT&T introduces common channel interoffice signaling, a protocol that allows software-controlled, networked computers or switches to communicate with each other using a band other than those used for voice traffic. Basically a dedicated trunk, the network separates signaling functions from the voice path, checks the continuity of the circuit, and then relays the information.
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1978 |
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Public tests of a new cellular phone system
Public tests of a new cellular phone system begin in Chicago, with more than 2,000 trial customers and mobile phone sets. The system, constructed by AT&T and Bell Labs, includes a group of small, low-powered transmission towers, each covering an area a few miles in radius. That test is followed by a 1981 trial in the Washington-Baltimore area by Motorola and the American Radio Telephone Service. The Federal Communications Commission officially approves commercial cellular phone service in 1982, and by the late 1980s commercial service is available in most of the United States.
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1990s (Mid) |
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Voice Over Internet Protocols
The advent of Voice Over Internet Protocols (VoIP)—methods of allowing people to make voice calls over the Internet on packet-switched routes— starts to gain ground as PC users find they can lower the cost of their long-distance calls. VoIP technology is also useful as a platform that enables voice interactions on devices such as PCs, mobile handhelds, and other devices where voice communication is an important feature.
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2000 |
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100 million cellular telephone subscribers
The number of cellular telephone subscribers in the United States grows to 100 million, from 25,000 in 1984. Similar growth occurs in other countries as well, and as phones shrink to the size of a deck of cards, an increasingly mobile society uses them not only for calling but also to access the Internet, organize schedules, take photographs, and record moving images.
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