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General Toll Switching Plan
The General Toll Switching Plan was a systematic nationwide effort by the American Telephone and Telegraph Company (AT&T) of organizing the telephone toll circuits and cable routes of the nation, and of streamlining the operating principles and technical infrastructure for connecting long-distance telephone calls in North America. This involved the design of a hierarchical system of toll-switching centers, a process that had found substantial maturity by 1929. The switching plan was principally operated by the ''Long Lines'' division of the Bell System in cooperation with independent telephone companies under the decree of the Kingsbury Commitment, reached with the United States government in 1913. The General Toll Switching Plan was a system manually operated by long-distance telephone operators. It was the forerunner of an automated system called Nationwide Operator Toll Dialing that was begun in 1943, which eventually led to Direct Distance Dialing (DDD) within the framework of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Telephone And Telegraph Company
AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile telephone services in the U.S. , AT&T was ranked 13th on the ''Fortune'' 500 rankings of the largest United States corporations, with revenues of $168.8 billion. During most of the 20th century, AT&T had a monopoly on phone service in the United States. The company began its history as the American District Telegraph Company, formed in St. Louis in 1878. After expanding services to Arkansas, Kansas, Oklahoma and Texas, through a series of mergers, it became Southwestern Bell Telephone Company in 1920, which was then a subsidiary of American Telephone and Telegraph Company. The latter was a successor of the original Bell Telephone Company founded by Alexander Graham Bell in 1877. The American Bell Telephone Company formed the American Tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Laboratories
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by multinational company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several laboratories in the United States and around the world. Researchers working at Bell Laboratories are credited with the development of radio astronomy, the transistor, the laser, the photovoltaic cell, the charge-coupled device (CCD), information theory, the Unix operating system, and the programming languages B, C, C++, S, SNOBOL, AWK, AMPL, and others. Nine Nobel Prizes have been awarded for work completed at Bell Laboratories. Bell Labs had its origin in the complex corporate organization of the Bell System telephone conglomerate. In the late 19th century, the laboratory began as the Western Electric Engineering Department, l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Public Sphere
The public sphere (german: Öffentlichkeit) is an area in social life where individuals can come together to freely discuss and identify societal problems, and through that discussion influence political action. A "Public" is "of or concerning the people as a whole." Public Sphere is a place common to all, where ideas and information can be exchanged. Such a discussion is called public debate and is defined as the expression of views on matters that are of concern to the public—often, but not always, with opposing or diverging views being expressed by participants in the discussion. Public debate takes place mostly through the mass media, but also at meetings or through social media, academic publications and government policy documents. The term was originally coined by German philosopher Jürgen Habermas who defined the public sphere as "''made up of private people gathered together as a public and articulating the needs of society with the state''". Communication scholar Ger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Line
In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmission must be taken into account. This applies especially to radio-frequency engineering because the short wavelengths mean that wave phenomena arise over very short distances (this can be as short as millimetres depending on frequency). However, the theory of transmission lines was historically developed to explain phenomena on very long telegraph lines, especially submarine telegraph cables. Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas (they are then called feed lines or feeders), distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses. RF engineers commonly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing In The PSTN
Routing in the PSTN is the process of forwarding telephone calls between the constituent telephone networks that comprise the public switched telephone network (PSTN). Telephone calls are routed across a network of potentially many switching systems, often owned by different telephone carriers. Switching systems are connected with trunks. Each switch may have many neighbors. Neighboring switches owned by different operators are connected at interconnect points. The PSTN is a network that uses destination routing to direct calls from origin to the recipient. It is not a full mesh network with the nodes of every operator directly connected to those of every other, which would be impractical and inefficient. Therefore, calls may be routed through intermediate operator networks before they reach their final destination. Efficient least-cost routing is an important procedure in PSTN routing. Call routing Each time a call is placed for routing, the destination number (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Original North American Area Codes
The original North American area codes were established by the American Telephone & Telegraph Company (AT&T) in 1947, following the demonstration of regional Operator Toll Dialing during the World War II period. The program had the goal of speeding the connecting times for long-distance calling by eliminating intermediary telephone operators. Expanding this technology for national use required a comprehensive and universal, continent-wide telephone numbering plan. The new numbering plan established a uniform destination addressing and call routing system for all telephone networks in North America which had become an essential public service. It had the eventual benefit of direct distance dialing (DDD) by telephone subscribers. The initial ''Nationwide Numbering Plan'' of 1947 established eighty-six numbering plan areas (NPAs) that principally followed existing U.S. state and Canadian provincial boundaries, but fifteen states and provinces were subdivided further. Forty NPAs wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carrier System
A carrier system is a telecommunications system that transmits information, such as the voice signals of a telephone call and the video signals of television, by modulation of one or multiple carrier signals above the principal voice frequency or data rate.Western Electric (1969) ''Fundamentals of Telephone Communication Systems'', p.16.2 Carrier systems typically transmit multiple channels of communication simultaneously over the shared medium using various forms of multiplexing. Prominent multiplexing methods of the carrier signal are time-division multiplexing (TDM) and frequency-division multiplexing (FDM). A cable television system is an example of frequency-division multiplexing. Many television programs are carried simultaneously on the same coaxial cable by sending each at a different frequency. Multiple layers of multiplexing may ultimately be performed upon a given input signal. For example, in the public switched telephone network, many telephone calls are sent over sha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Wire
Open wire was an early transmission technology in telecommunication, first used in telegraphy. It consisted of pairs of electric wire strung on a pole line between communities, towns, and cities. The wire of the transmission line was attached to the cross-arms of each pole with glass insulators.E.F. O'Neill (ed.), Bell Telephone Laboratories Staff,, ''A History of Engineering and Science in the Bell System–Transmission Technology (1925–1975)'' AT&T Bell Laboratories (1985), ISBN 0-932764-08-8, p.4 It was originally manufactured from iron or steel, but developments in annealing of copper made it possible to use this metal by the 1890s to reduce electrical resistance substantially. Copper wire was drawn to a diameter of up to 1/6 inch (165 mils). The glass insulators on the pole cross-arms were spaced at about 12 inches apart. Typically up to five wire pairs were installed on each crossarm, and multiple cross-arms could be installed on each pole. The practical limit in dista ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
First Transcontinental Telephone Call
A telephone call, which for marketing purposes is claimed to be the ''first transcontinental telephone call'', occurred on January 25, 1915, a day timed to coincide with the Panama–Pacific International Exposition celebrations. However, the transcontinental telephone line was first completed on June 17, 1914, and successfully first voice tested in July 1914. A 1998 U.S. postage stamp commemorates the completion of the line in 1914. Background The original long-distance telephone network actually started in 1885, in New York City. By 1892 this line reached Chicago. After introducing loading coils in 1899, the long-distance line continued west, and by 1911 it reached Denver, Colorado. The president of AT&T, Theodore Vail, committed the company to a transcontinental line in 1909. On June 17, 1914, after affixing of telephone line, workers raised the final pole at Wendover, Utah, actually on the border between Nevada and Utah state lines. Then, Theodore Vail, the president of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audion
The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906.De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is , Space Telegraphy', filed January 29, 1907, issued February 18, 1908 The link is to a reprint of the paper in the ''Scientific American Supplement'', Nos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350 and 354-356. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate. It is important in the history of technology because it was the first widely used electronic device which could amplify. A low power signal at the grid could control much more power in the plate circuit. Audions had more residual gas than later vacuum tubes; the residual gas limited the dynamic range and gave the Audion non-linear characteristics and erratic per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee De Forest
Lee de Forest (August 26, 1873 – June 30, 1961) was an American inventor and a fundamentally important early pioneer in electronics. He invented the first electronic device for controlling current flow; the three-element "Audion" triode vacuum tube in 1906. This started the Electronic Age, and enabled the development of the electronic amplifier and oscillator. These made radio broadcasting and long distance telephone lines possible, and led to the development of talking motion pictures, among countless other applications. He had over 300 patents worldwide, but also a tumultuous career— he boasted that he made, then lost, four fortunes. He was also involved in several major patent lawsuits, spent a substantial part of his income on legal bills, and was even tried (and acquitted) for mail fraud. Despite this, he was recognised for his pioneering work with the 1922 IEEE Medal of Honor, the 1923 Franklin Institute Elliott Cresson Medal and the 1946 American Institute of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Wire
Open wire was an early transmission technology in telecommunication, first used in telegraphy. It consisted of pairs of electric wire strung on a pole line between communities, towns, and cities. The wire of the transmission line was attached to the cross-arms of each pole with glass insulators.E.F. O'Neill (ed.), Bell Telephone Laboratories Staff,, ''A History of Engineering and Science in the Bell System–Transmission Technology (1925–1975)'' AT&T Bell Laboratories (1985), ISBN 0-932764-08-8, p.4 It was originally manufactured from iron or steel, but developments in annealing of copper made it possible to use this metal by the 1890s to reduce electrical resistance substantially. Copper wire was drawn to a diameter of up to 1/6 inch (165 mils). The glass insulators on the pole cross-arms were spaced at about 12 inches apart. Typically up to five wire pairs were installed on each crossarm, and multiple cross-arms could be installed on each pole. The practical limit in dista ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
