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. 
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.
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. Sound Motion Pictures
AT&T invented the technology that brought sound to Hollywood in the
1920s.
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.
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.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.
In 1949, the 20th anniversary of the invention of the coaxial cable system, Lloyd Espenschied (left) and Herman Affel reflect on the evolution of the cable. Espenschied holds a section of the early experimental coaxial cable that he and Affel developed; Affel holds a section of the type of cable that was being laid throughout the Bell System in the 1940s.
1940
- 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.
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.
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.
1946
- 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
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.
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