AT&T Labs Research — Leading Invention, Driving Innovation

Quantum Computing. Traditional computing is based on just two possibilities, 0 or 1, but quantum computing takes advantage of a subatomic particle’s simultaneous, multiple states to represent an array of possibilities that can be calculated simultaneously, while also taking probabilities into account. A working Quantum Computing model will dramatically increase the speed of information processing and will be a catalyst for breakthroughs in many fields.

1999

 

 

1998

Phone Web. Phone Web is an IVR alternative that allows customers to access the content and interactions of Web pages through a telephone. Phone Web uses Phone Markup Language (PML), a simple language that is an extension of HTML, and can be set up without highly skilled programmers. Calling a Phone Web system gains access through AT&T's inbound network services. Information is received by the Phone Web hardware, which retrieves the appropriate PML page, interprets that page, and sends back the response.

a2b Music. a2b Music cleared the way for major record labels, as well as traditional and online music resellers, to securely distribute digital music over the Internet while ensuring copyright protection. a2b leveraged two Research-developed technologies: the AT&T Proprietary Compression Algorithm and the trust management system PolicyMaker.

1997

 

 

1995

Video Indexing. Pioneering work on content-based sampling of video and automatic generation of searchable hypermedia documents from video programs paved the way for creating video search engines and searchable/browsable TV.

Machine Learning. Pioneered new breed of machine learning algorithms including Support Vector Machines and AdaBoost. These algorithms are the heart and soul of all machine-learning research worldwide. Today, they are being commonly used as large-margin classifiers for natural language processing and data mining.

UWIN. UNIX for WINdows, a UNIX to Windows integration toolkit that provides almost all the features of a traditional UNIX operating system.

The Computer Videophone. The Model 70 was the grandchild of the Picturephone, an AT&T Bell Labs idea-ahead-of-its-time dating from 1954. People didn't want to be seen on the phone in the 1950s (or the 1960s or the 1970s), but they did seem open to the idea of appearing on computer screens at work. The Model 70 not only made simultaneous video communication possible, it offered callers the ability to open, view, and edit files, as well as annotate and write comments on the screen with a mouse or keyboard commands.

1993

 

 

1992

Fault-Tolerance Software. Traditionally, large-scale, complex telephone switching operations used mainframes to ensure the reliability. But in 1992, an AT&T team developed an alternative: Fault-Tolerance Software. This software allows a telecommunications system to “tolerate” hardware faults, and some of the design and coding faults built into them, while continuing to function effectively. Easily embedded in any application, the system detects failures, backs up and recovers data, eases communications among processes, and automatically restarts and restores crashed programs in seconds. Fault tolerance software has use in any system where avoiding service outages is crucial, including Wall Street and ATMs.

AST Software Toolkit. An extensive collection of software tools and libraries portable to most known operating systems. The AST software is widely used by software developers around the world.

The Instant Language Translator. The Voice English/Spanish Translator was born in a hallway in 1989 when four AT&T Bell Labs engineers working on speech recognition and synthesis struck up a conversation with two visiting researchers from Telefonica Investigacion y Desarollo, the Spanish equivalent of AT&T Bell Labs. They quickly realized that their research provided all the components to create a real-time language translator.

Three years later, the VEST gave its first public demonstration. It recognized roughly 450 words in over a billion sentence combinations. It determined which language was being spoken, broke down sentences into grammatical components, and translated it as text — all in less than a second. Its language compiler collected grammar rules every time it performed a translation, helping the VEST to provide ever-faster and more accurate translations.

Voice Recognition Call Processing (VRCP). VRCP, the first nationwide voice-enabled service ushered in a new era of automated call center services for both AT&T and the telecom industry by automatically, reliably, and robustly automating a significant percentage of the ‘Operator Assisted’ 0+ calls in the AT&T network. Its simple five-word vocabulary—“calling card, collect, third party, person-to-person, and operator”—let customers use their voice instead of touch-tones to enter billing information. VRCP supported two patented technologies: “barge-in” used echo cancellation methods to allow customers to interrupt voice prompts and begin speaking at any time, and “wordspotting,” the capability to ignore extraneous speech, allowing commands such as “I want to make a calling card call, please”. AT&T’s innovations were adopted worldwide by all speech engine providers.

The VRCP service was launched in March 1992. Once fully deployed in the AT&T network, VRCP automated over 3 million phone calls per day, or over 1B calls per year, making it the most widely accessed speech recognition system in the world in its time. The service properly recognizes more than 99.5% of the calls. It was easily the most profitable speech recognition system in the world, having saved AT&T billions of dollars since deployment.

HDTV. HDTV is a big leap forward from the 1951 broadcast standards, with color and visual clarity approaching that of 35mm film and with CD-quality sound. However, HDTV requires high-speed signal processing and a receiver with enough specialized computer power to decode and expand HDTV signals. AT&T Bell Labs with its experience in high-speed digital switching is working to make HDTV work, and to assemble a simulation system for showing to the FCC.

The Speech-Driven Robot. The Speech-Actuated Manipulator (SAM) had one arm, two video cameras, eight computers, and could understand 300 billion sentences. Developed at Bell Labs, SAM was the product of research into computer speech recognition and machine intelligence. Commands were issued to SAM over a telephone. For commands it couldn’t understand, SAM in its own synthesized voice asked for an explanation, storing this new knowledge for future reference.

SAM is a first step toward complex machines that can understand natural language, such as automatic teller machines that converse with customers or machines that obey spoken commands to clean up hazardous wastes or deploy in deep space.

1989

 

 

1988

CIA. An architecture and system to store, process, and display relations among objects in C programs. CIA was used to analyze the entire 4ESS and 5ESS software systems which consisted of several million lines of code.

Perceptual Audio Coding. Jim Johnston demonstrates the first frequency domain audio coder that is based on analyzing what the ear can and can’t hear and then not coding the “perceptually irrelevant” frequencies. This concept was first put into a standardized use in MPEG Audio Layer 3, better known as MP3. It was later used in the MPEG Advanced Audio Coder known as AAC which was designed explicitly for stereo and multi-channel signals.

Automated Graph Drawing. AT&T Researchers proposed computable aesthetic criteria for drawing directed graphs and implemented DAG, the first automatic graph drawing program capable of rendering graphs with up to thousands of nodes and edges. This work led to GraphViz, a graph drawing toolkit widely used around the world.

Delta Compression. Introduction of a method for compressing an arbitrary data file given a related one. This enabled version control systems capable of storing any file types, not just text files. Delta compression now finds applications in diverse areas including speeding up web communication, reducing data storage, and others.

1987

 

 

1984

Dynamic Non-Hierarchical Routing. First deployment of Dynamic Non-Hierarchical Routing (DNHR) in any network.

Cellular Phones. AT&T Labs developed car phones in the 1940s and continued to seek improvements. But until recently mobile telephones were rare, limited by a lack of available communications channels. The big breakthrough came when AT&T Labs divided wireless communications into a series of cells, then automatically switched callers as they moved so that each cell could be reused. This led to the development of cellular phones and made today's mobile communications possible.

For their pioneering work in cellular telephony, AT&T Labs researchers Richard Frenkiel and Joel Engles earned the National Medal of Technology. Cellular telephony has spawned a multibillion-dollar industry and has freed tens of millions of people, both at home and at work, to communicate anywhere, any time.

C++. Tired of the lack of expressiveness of mainstream programming languages of the day and of the slowness of experimental languages, AT&T researcher Bjarne Stroustrup built the first version of C++ in 1983. C++ combines the expressive power of OOP (object-oriented programming) with the speed, compactness, and flexibility of C, its systems programming language predecessor, which was invented at AT&T ten years earlier. C++ matches C in efficiency and adds facilities for building larger, more easily maintained, and more reliable systems.

Stroustrup's creation, originally intended to improve the working lives of his colleagues, rapidly became one of the most influential programming languages in industry and academia worldwide. Today, upwards of a million programmers use C++ to write software for machines ranging from PCs to supercomputers. If you have used a computer, you have almost certainly used a program written in C++. Most PC and Internet users do so daily. C++ is even used for software in gadgets such as cameras and elevators, which are not usually associated with computers and programming.

At AT&T, C++ has become embedded in transmission, switching, and operations systems. C++ is also used in scientific programming, data analysis, simulation, and other mainstays of telecommunications research. Constant research and refinement have kept C++ in the front line of systems development to this day.

Ksh. An improved UNIX shell and the first shell command with full programming language features.

1983

 

 

1982

Interpretive Frame System (IFS). A high-level language and system for building end-user applications. Aside from shell scripting languages, IFS was one of the first languages to enable reuse of software tools in building applications.

Multipulse Linear Prediction. Bishnu Atal and Joel Remde demonstrated the first speech coder using a limited number of amplitude pulses for the excitation of a linear predictive filter to produce coded speech. This invention was followed in 1984 by another produced by Atal and Manfred Schroeder in which the excitation was selected from a fixed codebook. In both inventions, the excitation was selected using a perceptually based analysis-by-synthesis technique. All modern digital cellular speech coders are based on this technique.

Fiber Optic Communication. AT&T Bell Labs scientists became interested in lightwave communication in the mid-1960s, when it became apparent that lightwaves had an enormous capacity for carrying information and were immune from electrical interference. Advances in lasers, light-emitting diodes, repeaters, connectors, photodetectors and glass fibers in the following decades - and the realization that they could be fabricated and installed as integrated components - led to the installation of the first lightwave system in an operating telephone company in 1977.

This installation was the world's first lightwave system to provide a full range of telecommunications service - voice, data, and video - over a public switched network. The system, extending about 1.5 miles under downtown Chicago, used glass fibers that each carried the equivalent of 672 voice channels.

1977

 

 

1976

Epitaxy Microchips.The epitaxy fabrication process was invented in 1960 by J.J. Kleimack, H.H. Loar, I.M. Ross, and H.C. Theuerer. It was a new method for growing, on a silicon wafer, layer after layer of silicon films identical in structure with the wafer itself. Epitaxy made possible a tenfold increase in the operating speed of transistors.

Research into epitaxy continued as demand grew for multilayer semiconductors and semi-insulators. Increasingly precise film thicknesses were required for ever-faster processors, and to meet the need A.Y. Cho perfected Molecular Beam Epitaxy (MBE), an ultra-high vacuum technique that could produce single-crystal growth one atomic layer at a time.

MBE freed molecules of an element by heating it in an effusion oven. Some of these molecules would then escape into a chamber with a vacuum so intense that the freed molecules were drawn into a linear "beam." A substrate wafer was mounted in the center of this beam and the freed molecules could then be deposited, directly atop each other, one layer at a time.

First Digital Electronic Switching. In a major breakthrough for long-distance call completion time, AT&T launched the world?s first electronic digital switch, the 4ESS switch, in the Chicago network January 16, 1976.

The 4ESS, taking five years and costing over $400 million to design and build, could comfortably handle 500,000 calls per hour - 10 times the capacity of the electro-mechanical switch it replaced.

Customers noticed an immediate boost in service speed. The new switch combined with the related technology of common channel signaling dramatically improved long-distance completion time, which dropped from 10-20 seconds to a mere 1-2 seconds. The 4ESS delivered the intelligence, flexibility, and speed of a special purpose computer to the long-distance network.

The success of the 4ESS relied on a solid foundation going back to the 1930s, when AT&T research director Mervin Kelly challenged his team to find a solid-state replacement for electro-mechanical relays in telephone switches, up through the 1947 invention of the transistor, and the introduction into local service in 1965 of the first analog electronic switch, the 1ESS switch.

In 1999, AT&T installed the 145th and last 4ESS switch in the network.

Picturephone. The first Picturephone test system, built in 1956, was crude - it transmitted an image only once every two seconds. But by 1964 a complete experimental system, the "Mod 1," had been developed. To test it, the public was invited to place calls between special exhibits at Disneyland and the New York World's Fair. In both locations, visitors were carefully interviewed afterward by a market research agency.

People, it turned out, didn't like Picturephone. The equipment was too bulky, the controls too unfriendly, and the picture too small. But the Bell System was convinced that Picturephone was viable. Trials went on for six more years. In 1970, commercial Picturephone service debuted in downtown Pittsburgh and AT&T executives confidently predicted that a million Picturephone sets would be in use by 1980.

What happened? Despite its improvements, Picturephone was still big, expensive, and uncomfortably intrusive. It was only two decades later, with improvements in speed, resolution, miniaturization, and the incorporation of Picturephone into another piece of desktop equipment, the computer, that the promise of a personal video communication system was realized.

1970

 

UNIX and the Internet. 1969 will forever be remembered as the year of the "Miracle Mets" and Neil Armstrong's walk on the moon. But, as the Internet's influence continues to grow, maybe 1969 will come to be known as the "Year of the Internet" since it was 1969 that the Internet was launched. The development of the Internet has close ties to the UNIX operating system, which was developed at AT&T Labs. The Internet itself would not exist if it were not for AT&T's telecommunications network, the electronic gateway that connects you to the rest of the world.

Over the past 30 years, AT&T Labs has made many contributions to the development of the Internet and to computer software. Among the programming languages developed at AT&T Labs are C and C++.

1969

 

 

1967

LPC Analysis & Synthesis. Bishnu Atal invented linear prediction analysis and synthesis of speech. The linear prediction coefficients (LPC) became a very popular means for capturing the spectrum of speech and using it for analysis, synthesis and speech compression. This spectral analysis technique is used in every cellular speech coder standard that has ever been created.

The Echo of the Big Bang. A.A. Penzias and R.W. Wilson were conducting radio astronomy experiments with the ultra-sensitive horn antenna at Crawford Hill, but were frustrated by a noise in its receiving system, a noise that remained constant no matter which direction they scanned. This made no sense and they suspected that it came from bird droppings on the antenna, but after a careful cleaning the noise remained. They then realized that the noise corresponded exactly with the "background radiation" posited by cosmologists who favored the Big Bang theory of creation. Penzias and Wilson had heard the Echo of Creation, and were awarded a Nobel Prize for their discovery.

1965

 

 

1962

Satellite Transmission. The first television picture relayed from earth to space and back occurred on July 10, 1962. The transmission, which showed the American flag waving in front of the Earth Station in Andover, Maine, was made possible when NASA launched AT&T's Telstar, the world's first active communications satellite, at four thirty-five that morning.

The idea of an active satellite, which doesn't simply reflect signals but amplifies and retransmits them, was conceived by science-fiction writer Arthur C. Clarke in 1945. And in 1955, John Pierce of Bell Telephone Laboratories sketched the possibilities for satellite communications in a scientific paper. Two years later, the Russians launched Sputnik, and the space race began. The National Aeronautics and Space Administration (NASA) soon began launching American satellites.

Pierce, meanwhile, had convinced AT&T management to proceed. In January 1960, AT&T and NASA agreed to a joint project. AT&T would design and construct an experimental satellite and pay NASA to launch it. It would be the first privately sponsored space launch.

Researcher Eugene O'Neill led a team at Bell Telephone Laboratories that designed Telstar, a 34 1/2-inch, 170-pound satellite that fit NASA's Delta rocket. Telstar would receive microwave signals from a ground station, amplify them and rebroadcast them. The team calculated an orbital path the rocket could reach, and located an ideal site for the U.S. ground station near Andover, Maine.

Here they built a massive 160-foot-diameter horn antenna, protected from the elements by the largest air-supported structure ever built. And on that morning in July 1962, the team held its collective breath as countdown led to a perfect blastoff. Telstar was in space.

That evening, AT&T President Frederick Kappel picked up a phone in Andover and placed a call. Vice President Lyndon Johnson in Washington, D.C., answered. The call - the first ever transmitted through space - was relayed via Telstar. Within 30 minutes, Telstar produced several other firsts: successfully transmitting faxes, high- speed data, and both live and taped television. Portions of the television transmission were successfully received in France — the first live transmission of television across an ocean.

More elaborate television demonstrations followed later that month, including countries from Norway to Italy sending programs westward, and the United States sending programs east.

Telstar went out of service on Feb. 21, 1963, its mission accomplished. After a second successful experiment, Telstar II, AT&T retired from the field of satellite development and concentrated on leasing bandwidth for use in international telephony.

Communications Satellites. Until the 1960s, voice communications between North America and the other continents was possible - but expensive. Then AT&T Labs launched Echo, a giant, experimental balloon off of which messages could be bounced. Two years later Telstar was sent into orbit, the world's first active communications satellite.

For the next two decades, communications satellites played a major role in expanding both international and domestic long distance calling and television transmission. Today most long distance calls are carried by fiber optics and submarine cable, but communications satellites play an increasing role in television transmission, including direct broadcasts to home satellite dishes with digital television.

1960

 

The Laser. Almost all modern communications, including everything from cable television to the Internet, are carried on digital pulses of focused, high-intensity light called the "laser." Beginning in the late 1950s, AT&T Labs worked extensively to develop the laser into a useful device.

The laser couldn't send information anywhere if there wasn't a communications system to carry it. So AT&T coupled the laser with transmission lines of hair-thin, super-transparent, ultra-strong glass fiber which today carry tens of billions of information bits every second.

Lasers and fiber optic cable have been used extensively in the United States since the early 1980s. Over the past decade, AT&T has installed undersea fiber optic cable connecting the United States to most of the industrialized nations of the world.

1958

 

 

1956

Transoceanic Telephone Cables. Today, international calling is routine, with a half-million transatlantic calls from the United States every day. But it took years of effort by AT&T scientists and engineers to make it so. They began to study deep-sea, long-distance submarine cable as an alternative to the telegraph and short wave radio in the early 1930s.

Transoceanic telegraph cables have been around for almost 100 years, but the more delicate voice signals with their higher frequencies could not make it across the ocean without a periodic boost to the voice signal. Thus the challenge was to design amplifiers installable three miles below the ocean surface and capable of operating for many years without requiring a repair. Built around an electron tube especially developed for this purpose, the amplifiers or repeaters, encased in flexible multi-metal housings, were spaced at 4-mile intervals along the cable. The cable also had an outer sheath of armor wires to provide strength and protection against abrasion and an extra copper sheath to keep out marine worms, which were known to plague telegraph cables.

Laying each of the two cables that made up the systems (one for each direction of communication) took weeks and was carried out during two consecutive summers. The first day of commercial service, September 26, 1956, saw a 75 percent increase in transatlantic telephone traffic.

The Solar Cell. In the early 1950s R.S. Ohl discovered that sunlight striking a wafer of silicon would produce unexpectedly large numbers of free electrons. In 1954, G.L. Pearson, C.S. Fuller, and D.M. Chapin created an array of several strips of silicon (each about the size of a razor blade), placed them in sunlight, captured the free electrons and turned them into electrical current. This was the first solar battery. It could convert only six percent of the sunlight into useful energy; people wondered what it was good for. Today, the solar cells we use to power calculators, highway emergency phones, and satellites can convert over 25 percent of the sunlight that hits them into useful energy.

1954

 

 

1951

Microwave Radio-Relay Skyway. August 17, 1951: The first telephone call is placed on AT&T's new microwave radio-relay skyway, the first facilities to transmit telephone conversations across the United States by radio rather than wire or cable.

The new backbone telephone route, at the time the longest microwave system in the world, relayed calls along a chain of 107 microwave towers, spaced about 30 miles apart. AT&T spent about three years building it at a cost of $40 million.

The system was designed to carry television signals as well as telephone messages, and less than three weeks after the first phone call, it did just that. On Sept. 4, the largest single television audience to date - estimated at more than 30 million people - saw and heard President Harry Truman open the Japanese Peace Treaty Conference in San Francisco. The nation's first coast-to-coast telecast, this broadcast was made possible when AT&T met a U.S. State Department request to advance the TV opening of the new system by a month.

The historic program went off without a hitch. The New York Times reported that "the image reproduced on screens in the New York area, nearly 3,000 miles from the scene, had excellent clarity and compared favorably with programs of local origin. The contrast was of first-rate quality and there was no distortion."

In a letter to AT&T President Cleo Craig, Federal Communications Commission Chairman Wayne Coy wrote, "Moving forward the date for the opening of the transcontinental microwave radio relay for television - makes your accomplishment all the more significant. I appreciate the zeal, the enterprise and all the extra effort that made this triumphant event in communications history possible."

First Direct-Dial Transcontinental Telephone Call. Nov. 10, 1951: Mayor M. Leslie Downing of Englewood, N.J., picked up a telephone and dialed 10 digits. Eighteen seconds later, he reached Mayor Frank Osborne in Alameda, Calif. The mayors made history as they chatted in the first customer-dialed long-distance call, one that introduced area codes.

The inauguration of Direct Distance Dialing eliminated the need for a "number, please" operator, accelerated connection speed, and cut the cost of long-distance calls. While direct-dialing had been available since the 1930s within some small areas, Direct Distance Dialing launched a service that ultimately connected users through thousands of switches across North America.

The mayors' call proved a vast improvement over the first transcontinental telephone call 36 years earlier, when it took five operators 23 minutes to set up a call from San Francisco to New York. For many years, long-distance calls required an operator at the calling end and another at the receiving end. More operators were often needed at intermediate points to build the route through the network one segment at a time.

In 1943, AT&T installed the first automatic toll switch, a number 4 crossbar, in Philadelphia, enabling one operator to complete a long-distance call. But the operator might still dial up to 12 digits of routing codes to build the route to the destination, then dial the local phone number, another four to seven digits.

Determined to build a better system, an AT&T Engineering Department team investigated using a single set of short codes to divide North America into unique calling areas. The team?s L. K. Palmer and W. H. Nunn concluded that a three-digit code - 2-to-9 as the first digit, the second number always 1 or 0 - produced a set of unique area codes with room for growth. Back then, a local phone number started with an exchange name followed by numbers, such as "Murray Hill 5." Since there were no letters above 1 or 0 on the dial, no phone numbers used a 1 or 0 in the first two pulls of the dial. Thus, equipment could distinguish long distance from local calls.

The team assigned area codes with a middle digit of 1 to states needing multiple area codes and area codes with a middle digit of 0 to the rest. Operators memorized area codes. To make the system work, local numbers, which varied in length, began changing to a single pattern - two letters and five numbers, as used in the largest cities. All long-distance calls would be 10 digits.

Shortly after operators began using area codes, AT&T tested its new system, with help from the mayors. Englewood (area code 201) called Alameda (area code 415). The trial being a success, AT&T rolled out Direct Distance Dialing across America. Ninety area codes in 1951 grew to 135 in 1991. In recent years, cellular phones, fax machines, modems, and local service competition ignited explosive area-code growth. The last code available in the original scheme - 610 - entered service in Pennsylvania in 1994. Codes with second digits other than 0 or 1 came into use. Today, there are 251 area codes...and counting!

Information Theory. In 1948, C.E. Shannon published an article titled "The Mathematical Theory of Communication," which quickly became known as Information Theory. IT made it possible to determine the theoretical limit of any channel's information-carrying capacity. Using IT as a mathematical benchmark, engineers were finally able to provide efficient, error-free transmission over noisy channels. IT also made possible the development of digital systems, which handle information, voice, data, and video in streams of coded pulses. Without Information Theory, the Web would not exist.

Four years after he published his ground-breaking theory, Shannon invented an electrical mouse with a telephone relay switch brain. Its ability to find its way through a maze demonstrated that computers could learn, a startling revelation to those who, until then, had used them only as giant adding machines.

Error Correction. Error-detecting coding, first developed for telephone switching, is now used throughout the computing and telecommunications industries. In 1948 , R.W. Hamming (left) of Bell Labs developed a general theory for error-correcting schemes in which "check-bits" are interspersed with information bits to form binary words in patterns. When a single error occurs in transmission, the word becomes invalid, but the error is automatically located and corrected.

1948

 

 

1947

The Transistor. The transistor, more than any other single development, made possible the marriage of computers and communication. Three AT&T Labs researchers - John Bardeen, William Shockley, and Walter Brattain - shared the Nobel Prize for their 1947 invention of this tiny, reliable, electronic component.

In the years following its creation, the transistor gradually replaced the bulky, fragile vacuum tubes that had been used to amplify and switch signals. The transistor - and the eventual creation of integrated circuits that contained millions of transistors - served as the foundation for the development of modern electronics.

First Mobile Telephone Call. June 17, 1946 - A driver in St. Louis, Mo., pulled out a handset from under his car's dashboard, placed a phone call and made history. It was the first mobile telephone call.

A team including Alton Dickieson and D. Mitchell from Bell Labs and future AT&T CEO H.I. Romnes, worked more than a decade to achieve this feat. By 1948, wireless telephone service was available in almost 100 cities and highway corridors. Customers included utilities, truck fleet operators and reporters. However, with only 5,000 customers making 30,000 weekly calls, the service was far from commonplace.

That "primitive" wireless network could not handle large call volumes. A single transmitter on a central tower provided a handful of channels for an entire metropolitan area. Between one and eight receiver towers handled the call return signals. At most, three subscribers could make calls at one time in any city. It was, in effect, a massive party line, where subscribers would have to listen first for someone else on the line before making a call.

Expensive and far from "mobile", the service cost $15 per month, plus 30 to 40 cents per local call, and the equipment weighed 80 pounds. Just as they would use a CB microphone, users depressed a button on the handset to talk and released it to listen.

Improved technology after 1965 brought a few more channels, customer dialing and eliminated the cumbersome handset. But capacity remained so limited that Bell System officials rationed the service to 40,000 subscribers guided by agreements with state regulatory agencies. For example, 2,000 subscribers in New York City shared just 12 channels, and typically waited 30 minutes to place a call. It was wireless, but with "strings" attached.

The Cellular Solution

Something better — cellular telephone service — had been conceived in 1947 by D.H. Ring at Bell Labs, but the idea was not ready for prime time. The system comprised multiple low-power transmitters spread throughout a city in a hexagonal grid, with automatic call handoff from one hexagon to another and reuse of frequencies within a city. The technology to implement it didn't exist, and the frequencies needed were not available. The cellular concept lay fallow until the 1960s, when Richard Frenkiel and Joel Engel of Bell Labs applied computers and electronics to make it work.

AT&T turned their work into a proposal to the Federal Communications Commission (FCC) in December 1971. After years of hearings, the FCC approved the overall concept, but licensed two competing systems in each city.

In 1978, AT&T conducted FCC-authorized field trials in Chicago and Newark, N.J. Four years later, the FCC granted commercial licenses to an AT&T subsidiary, Advanced Mobile Phone Service Inc. (AMPS). AMPS was then divided among the local companies as part of the planning for divestiture. Illinois Bell opened the first commercial cellular system in October 1983. AT&T re-entered the cellular business by acquiring McCaw Cellular in 1994, the same year that President Clinton awarded Frenkiel and Engel the National Medal of Technology.

Today, AT&T Wireless (AWS) operates one of the largest digital wireless networks in North America. With more than 17 million subscribers, including partnerships and affiliates, and revenues exceeding $10 billion, AT&T Wireless is committed to being among the first to deliver the next generation of wireless products and services. AWS offers customers high-quality wireless communications services, whether mobile or fixed, voice or data, to businesses or consumers, in the United States and internationally.

1946

 

 

1941

Touch Tone Telephones. The first touch-tone system - which used tones in the voice frequency range rather than pulses generated by rotary dials - was installed in Baltimore, Maryland, in 1941. Operators in a central switching office pushed the buttons; it was much too expensive for general use. However, the Bell System was intrigued by touch-tone because it increased the speed of dialing.

By the early 1960s, low-cost transistors and associated circuit components made the introduction of touch-tone into home telephones possible. Extensive human factors tests determined the position of the buttons to limit errors and increase dialing speed even further. The first commercial touch-tone phones were a big hit in their preview at the 1962 Seattle World's Fair.

Complex Number Generator. The first demonstration of remote computing took place on Sept. 11, 1940. George Stibitz, of AT&T's Bell Telephone Laboratories, demonstrated his Complex Number Calculator, the world's first electrical digital computer, to the American Mathematical Society at a meeting at Dartmouth College in Hanover, New Hampshire A teletypewriter was installed in a lecture hall at Dartmouth and connected via a modified teletypewriter line to Stibitz's electromechanical computer in New York. An attendant at the keyboard entered equations suggested by meeting attendees. The messages traveled down the circuit to New York, and the answers were returned to the teletypewriter via the same route

1940

 

High Frequency Radar. Radar, in principle, had been known since the mid-1930s, but it was a practical nightmare, requiring huge antennas to attain even satisfactory accuracy. The U.S. Navy asked AT&T Bell Labs for help in extending radar to higher frequencies, which would permit sharper beams and, thereby, smaller antennas. AT&T Bell Labs began its tests in 1939 , tracking ship movements from a hilltop along the coast of New Jersey. This resulted in the Mark 1, the first production high-frequency radar, which was installed on its first U.S. Navy warship in June, 1941. High-frequency radar, by the way, is a direct ancestor of the microwave oven.

The Digital Computer. In 1937, George Stibitz decided that the electromechanical relays that were the chief components in telephone switching systems could be used for another purpose. From the relays, flashlight bulbs, and a switch made from a tobacco tin, he built the first binary adder.

In 1939 , Stibitz and S.B. Williams built the Complex Number Calculator, the world's first electrical digital computer. Its brain consisted of 450 telephone relays and 10 crossbar switches, and it could find the quotient of two eight-place complex numbers in about 30 seconds. Three teletypewriters provided input to the machine.

In 1940, Stibitz took one of the teletypewriters to an American Mathematical Association meeting at Dartmouth, New Hampshire, and used it to communicate over phone lines with the Complex Number Calculator in New York. This was the world's first demonstration of remote computing.

The CNC, later renamed the Model 1 Relay Computer, remained in operation until 1949.

1939

 

 

1936

Synthetic Speech. Since its earliest days, Bell Labs had been concerned with the properties and analysis of human speech. It was inevitable that a Bell Labs scientist would invent an artificial talking machine and, in 1936, H.W. Dudley did. Photo: Electronic speech synthesizer. It was the world's first electronic speech synthesizer, and it required an operator with a keyboard and foot pedals to supply "prosody" ? the pitch, timing, and intensity of speech. Dudley called his device the "voice coder" though it quickly became known as, simply, "Voder." It was a hit at the New York and San Francisco World's Fairs of 1939.

Radio Astronomy. K. Jansky came to AT&T Bell Labs specifically to study noise. Overseas radiotelephone service had just begun and knowing more about noise ? the static that infested the airwaves ? was important. A large antenna that swiveled on a circular track, built in a New Jersey field far from city-made electrical interference, became Jansky's home. He began listening and taking notes.

After five years, Jansky published his findings. Noise always increased when he pointed his antenna at the Milky Way's center, and he therefore concluded that noise came from stars. The implications of this discovery were startling. Jansky had discovered a new tool one that could penetrate space, dust, and planetary clouds ? with which astronomers could probe the mysteries of space.

Yet Jansky received no accolades from the scientists of his day. His "star noise" went largely unappreciated, and he died in relative obscurity at the age of 44.

Radio astronomy later enabled AT&T researchers to hear the echo of the Big Bang.

Stereo Recordings. Prior to 1931, most phonograph records were produced by laterally cutting vibrations into wax disks. An AT&T research team led by Arthur C. Keller devised a technique that used vertical (or hill-and-dale) cutting, which resulted in better stylus tracking, lower harmonic distortion, a wider frequency response, and a longer playing time. The 1930s were an inopportune time to introduce a new consumer technology, so the vertical cut records achieved commercialization chiefly as the first technology for pre-recorded radio programs.

In 1933, A.C. Keller and I.S. Rafuse were conducting experiments into reducing phonograph recording intermodulation distortion. They decided to try two-channel recording. This led to the first U.S. single-groove stereo recording system in 1940.

AT&T also pioneered Electrical Recording.

1933

 

The Artificial Larynx. The first artificial larynx developed by AT&T Bell Labs was purely mechanical. A metallic reed vibrated inside a tube that was connected, by the speaker, between the mouth and the stoma, an artificial opening in the speaker's throat. Air forced up the windpipe, through the tube and across the reed, was then manipulated in the speaker's mouth to create artificial speech.

In 1960, AT&T Bell Labs replaced the mechanical artificial larynx with an electronic version. This required no stoma, and could simply be held against the speaker's throat. A vibrating driver in the larynx replaced the sounds made by vocal cords, which could then be formed into words by the speaker. AT&T made it available at cost worldwide.

Broadband Coaxial Cable. May 23, 1929 - Lloyd Espenschied and Herman Affel applied for a patent for broadband coaxial cable, the first broadband transmission medium.

By the early 1920s, AT&T engineers recognized that the open wire and cable in use at the time would be unable to carry the high frequencies needed for the broadband systems of the future. So Espenschied and Affel developed a new kind of wire system that could transmit a continuous range of high frequencies over long distances.

This revolutionary transmission system was based on the use of a coaxial conductor: two concentric cylinders of conducting material separated mainly by air. This structure reduced frequency losses and provided freedom from outside interference.

Espenschied and Affel were granted a patent in 1931. And in November 1936, the first voice transmission was made over coaxial cable installed between New York and Philadelphia.

The introduction of broadband coaxial cable made possible not only higher-capacity long distance circuits, but also intercity transmission of moving images, which paved the way for television.

1929

 

 

1927

Transatlantic Phone Service. Bell System engineers achieved the first voice transmission across the Atlantic, connecting Virginia and Paris briefly in 1915. A year later, they held the first two-way conversation with a ship at sea, and in 1926, the first two-way conversation across the Atlantic. On January 7, 1927, commercial telephone service (using radio) began between New York and London. Over the next several years, service spread throughout North America and Europe. In 1929, the S.S. Leviathan became the first ocean liner to offer radio telephone service to its passengers and crew. Pacific service began to Hawaii in 1931 and Tokyo in 1934. AT&T celebrated international service in 1935 with the first round-the-world telephone call. The two speakers, AT&T President W.S. Gifford and Vice President T. Miller, were in rooms in the same building, but their voices traveled on a circuit around the globe.

Transoceanic phone service was eventually handled by submarine cables and communications satellites.

Long Distance TV Transmission. In 1927, the Bell System sent live TV images of Herbert Hoover, then the Secretary of Commerce, over telephone lines from Washington, D.C. to an auditorium in Manhattan. It was the first public demonstration in the U.S. of long-distance television transmission.

Television in those days was mechanical. Hoover was scanned by a narrow beam of light passing through tiny holes in a large, spinning disk that was set in front of his face. The image appeared in New York as tiny dots of light on the 2x2.5 inch face of a neon glow lamp. The picture tube hadn't been invented yet.

Long-distance TV transmission was an offshoot of H.E. Ives and F. Gray's fax technology. If still images could be sent over a wire, why not moving images?

The Wave Nature of Matter. In the first quarter of the twentieth century, physicists had come to believe that on the subatomic level, matter and energy were different aspects of the same phenomena. But there was no experimental support for this theory until 1927 when C.J. Davisson and his assistant, L.H. Germer, began investigating electron emission in vacuum tubes. Davisson directed a particle beam of electrons at a crystal of nickel and measured the pattern and energy of the electrons that returned. He found that the reflected electrons were not randomly scattered at lower energy, as would be the case with particles bouncing off the crystal, but returned with no loss of energy in a pattern that could only be described as a diffraction of waves. This discovery - that matter sometimes behaved as waves - helped to revolutionize thinking in theoretical physics and earned Davisson a Nobel Prize.

Negative Feedback. In 1927, Harold Black proposed a novel technique for correcting instability and distortion in the process of amplifying communications signals. Called "negative feedback," the technique requires that part of the signal coming out of the amplifier be fed back and compared with the input signal. Distortions introduced by the amplifier are thus precorrected and largely eliminated. As a result, the amplifier can be made almost distortionless, despite fluctuations in the power supply and performance of electronic components.

Sound Motion Pictures. AT&T invented the technology that brought sound to Hollywood in the 1920s.Photo: 1920s Hollywood camera crew. Originally, sound for a motion picture was recorded on disks, then replayed on a large turntable that was synchronized with a film projector. Warner Brothers became the first studio to adopt the new technology, calling it "Vitaphone." In 1926, Warners Brothers premiered Don Juan, the first full length Vitaphone film, and the first with a synchronized sound track of music and audio effects. A year later, The Jazz Singer became the first feature with synchronized singing and dialog. By the early 1930s, sound-on-disk had given way to sound-on-film, which was easier to edit and exhibit. AT&T pioneered in sound-on-film as well.

1926

 

 

1924

Electrical Sound Recording. In 1924, J.P. Maxfield and H.C. Harrison of AT&T devised the first recording and reproducing system using electricity. Earlier systems had used direct conversion between sound and mechanical energy only. Photo: Early electrical sound recording machine. Using microphones and amplifiers, they extended the reproducible sound range by more than an octave and appreciably improved fidelity. The recording industry adopted electrical recording in 1925 . Victor records popularized AT&T's technology under the name "Orthophonic."

Four years later, an AT&T Bell Labs group headed by H.A. Frederick discovered that surface noise on records was caused by graphite on the wax master, which was routinely deposited to provide a conducting surface for electroplating. A.C. Keller and A.G. Russell discovered that sputtering gold on the master record eliminated this surface noise. This technique was soon adopted for motion picture and broadcast sound recordings and, after WWII, for phonograph records.

AT&T also pioneered hi fi and stereo recording.

Fax Service. In 1918 H. Nyquist began investigating ways to adapt telephone circuits for picture transmission. By 1924 this research bore fruit in "telephotography" - AT&T's fax machine.

The principles used in 1924 were the same as those used today, though the technology was comparatively crude. A photographic transparency was mounted on a spinning drum and scanned. This data, transformed into electrical signals that were proportional in intensity to the shades and tones of the image, were transmitted over phone lines and deposited onto a similarly spinning sheet of photographic negative film, which was then developed in a darkroom. The first fax images were 5x7 photographs sent to Manhattan from Cleveland and took seven minutes each to transmit.

 

The First Air-to-Ground and Ground-to-Air Radio Communications. July 1917: The first air-to-ground and ground-to-air radio communications were accomplished by AT&T engineers at Langley Field in Virginia.

In the early days of aviation, pilots relied upon primitive means of communication during flight, including hand signals and flags. But during World War I, the U.S. military desperately needed radio communication between airplanes and the ground and between the planes themselves.

So in May 1917, General George Squier of the U.S. Army Signal Corps contacted Western Electric, AT&T's manufacturing subsidiary, to request an airplane radio telephone with a 2,000-yard range. On June 5, AT&T engineers met with the military to gather technical requirements, only to discover that there was practically no information about such essentials as the wavelengths desired, antennas and power supplies.

Undaunted and spurred on by wartime urgency, AT&T engineers designed the equipment using solid hunches, available circuitry and a few field tests. On July 2, they made their first air-to-ground transmission over a distance of about two miles. And on July 4, they accomplished a ground-to-air transmission over the same distance. By August 20, they had achieved two-way communication between planes in flight. Western Electric began shipping radio telephone sets abroad in October.

Although few of those sets ever actually saw service, AT&T had proved that rapid voice communication between military vehicles in the air or on the sea was possible.

1917

 

 

1916

Remembering Claude Shannon. Claude Shannon has been described as the "intellectual giant of the digital age." By the time of his death on Feb. 24, 2001, Shannon had collected a pile of prestigious prizes that proved it — the National Medal of Science, Japan's Kyoto Prize, the IEEE Medal of Honor among them. But, none of those awards quite measured up to the honor he received in October 1998, when AT&T Labs named its two-building, 387,000-square-foot complex in Florham Park, N.J., the Shannon Laboratory.

Perhaps that building's sign should have read "Shnon Lab," because as the Father of Information Theory, Shannon paved the path for digital communications by introducing ingenious concepts for efficiently packaging and transmitting data.

Birth of the theory

Considered the Magna Carta of communication, Shannon's Information Theory first appeared more than 50 years ago in his 1948 Bell System Technical Journal paper "The Mathematical Theory of Communication."

Information Theory describes an ideal communications system in which all information sources -- people speaking, computer keyboards, video cameras -- have a "source rate" measured in bits per second. The channel through which the source's data travels has a "capacity," also measured in bits per second. Information can be transmitted only if the source rate does not exceed the channel's maximum capacity, now known as the Shannon limit.

To approach the Shannon limit, communications engineers encode data, compress it to remove redundancy, and transmit only information essential to understanding. By posting the sign "Shnon Lab," for example, we would eliminate predictable, redundant symbols and send only those symbols that contain unpredictable news -- what Shannon called "information."

It sounds simple, but the complex mathematical formulas embedded in Information Theory have guided the discoveries of two generations of communications engineers. "Information Theory stimulated all kinds of intellectual energy," says AT&T Fellow Neil Sloane, whose research on the mathematical framework of communications is rooted in Information Theory. "Without Shannon's theory, we wouldn't have all the digital devices we depend on today -- wireless phones, fax machines, compact disks or the Internet." Shannon's ideas have even been applied in such diverse fields as psychology, linguistics, economics and biology.

"Because Information Theory was such a profound development, history will remember Shannon as one of the great thinkers in the field of electrical engineering," says AT&T Fellow Larry Greenstein, who relied on Shannon's theories in researching point-to-point radio and wireless communication channels. "He broke the mold in the field of communications and did something unlike anything that came before -- not just an extension or improvement."

The cycling scholar

Just as unique as the theory was the theorist himself. Born in 1916, Michigan native Shannon arrived at AT&T in 1941 after producing what's been called the century's most important master's thesis and earning a Ph.D. at the Massachusetts Institute of Technology. His work on anti-aircraft and digital-encryption systems during World War II planted the seeds for Information Theory. Shannon reasoned that the same types of digital codes that protect sensitive information could be used to safeguard it from noise, static or interference.

While pondering such deep thoughts, Shannon often pedaled a unicycle through the halls of Bell Labs. In the early 1950s, his intellectual journey veered toward the relationship between people and machines, and he helped found the field of artificial intelligence. Among the first applications he devised in this area was Theseus, a mechanical mouse that solved mazes in search of a brass "cheese." During this period, Shannon also published one of the earliest proposals for a chess-playing computer.

By "teaching" an electrical mouse to find its way through a maze, Shannon helped stimulate Bell Labs researchers to think of new ways to use the logical powers of computers for operations other than numerical calculation.

After leaving AT&T in 1956, Shannon joined the faculty at MIT. He formally retired in 1978 and pursued his longtime passions — gadgets and juggling. In fact, one of his favorite creations was a juggling gadget — a robot in the likeness of comedian W.C. Fields.

"I've always pursued my interests without much regard to financial value or value to the world. I've spent lots of time on totally useless things," Shannon said in 1983, perhaps referring to such gizmos as a gasoline-powered pogo stick, a rocket-powered Frisbee, and THROBAC (THrify ROman numerical BAckward-looking Computer), a computer that calculates in Roman numerals.

"He had a wonderful sense of humor and was a great builder of gadgets," Sloane says. "His house was filled with toys, including one device that displayed all the gowns he wore to receive his dozen or more honorary doctorates. He hung them on a circular clothes line, and when he'd flip a switch, the gowns marched around and around."

The man who caused so much excitement died quietly at age 84. But in one of his last papers, Shannon continued pointing the way toward communications' far horizons: "Our government might consider ... listening for evidence of intelligent life on other star systems. Who knows, perhaps E.T. would have words of wisdom for all of us."

• Claude Shannon's Collected Papers
• Claude Shannon's Biography

First Transcontinental Telephone Call. Jan. 25, 1915 - If you collect U.S. postage stamps, you might have noticed one issued in February 1998 to commemorate AT&T's 1914 construction of the first transcontinental telephone line.

AT&T began building the nation's original long distance network in 1885. Starting from New York, the network reached Chicago in 1892. But, because an electrical signal weakens as it travels down a wire, that distance was close to the limit for a line built of thick copper. With the 1899 introduction of loading coils, which slow the rate at which a signal weakens, construction proceeded west. By 1911, the network stretched as far as Denver, but had reached the distance limit for loading coils.

In 1908, AT&T President Theodore Vail had made a transcontinental telephone line a major goal, even though he knew the technology to build one did not exist. The next year, Chief Engineer John J. Carty raised the stakes when he announced in San Francisco that AT&T would open a transcontinental line in time for the city's 1915 exposition to mark the completion of the Panama Canal.

But, without a scientific breakthrough, AT&T couldn't make good on that bet. To improve the company's odds, Carty not only hired physicist Dr. Harold Arnold to study the amplification of electrical signals, he also spread the word in the scientific and electrical-engineering community that AT&T would pay handsomely for an electrical amplifying device.

On Oct. 30, 1912, independent inventor Dr. Lee de Forest brought the audion, a three-element vacuum tube, to AT&T's engineering department. De Forest's invention provided a small amount of amplification, and then broke down into a bright blue haze. However, Arnold recognized almost immediately that the blue haze was caused by ionization of residual gasses in the tube. If he increased the vacuum, thereby removing most of the residual gasses, the audion would become a practical amplifier. So on Arnold's recommendation, AT&T bought the patent rights from de Forest.

By summer 1913, AT&T had tested high-vacuum tubes on the long distance network. And that fall, the company began constructing the line west from Denver and upgrading the line to the east. On June 27, 1914, AT&T completed the line, erecting the last pole at Wendover, Utah.

Only one problem remained: AT&T had connected the continent before the Panama-Pacific exposition was ready. So the company waited, and on Jan. 25, 1915, opened the line with great fanfare and celebrations in San Francisco and New York.

1915

 

The Telephone. On March 10, 1876, the telephone was born when Alexander Graham Bell called to his assistant, "Mr. Watson! Come here! I want you!" He was not simply making the first phone call. He was beginning a revolution in communications and commerce. It spread a web of instantaneous information across towns, then a continent, then the world, and has greatly accelerated economic development.

Learn more about the invention of the telephone.

1876