The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over 100 years from its creation in 1877 until its antitrust breakup in 1983. The system of companies was often colloquially called Ma Bell (as in "Mother Bell"), as it held a vertical monopoly over telecommunication products and services in most areas of the United States and Canada. At the time of the breakup of the Bell System in the early 1980s, it had assets of 150billion(equivalentto billion in ) and employed over one million people.
Beginning in the 1910s, American antitrust regulators had been observing and accusing the Bell System of abusing its monopoly power, and had brought legal action multiple times over the decades. In 1974 the Antitrust Division of the U.S. Department of Justice brought a lawsuit against Bell claiming violations of the Sherman Act. In 1982, anticipating that it could not win, AT&T agreed to a Justice Department-mandated consent decree that settled the lawsuit and ordered it to break itself up into seven "Regional Bell Operating Companies" (known as "The Baby Bells"). This ended the existence of the conglomerate in 1984. The Baby Bells became independent companies and several of them are large corporations today.
In 1877, the American Bell Telephone Company, named after Alexander Graham Bell, opened the first telephone exchange in New Haven, Connecticut. Within a few years local exchange companies were established in every major city in the United States. Use of the Bell System name initially referred to those early telephone franchises and eventually comprised all telephone companies owned by American Telephone & Telegraph, referred to internally as associated companies, regional holding companies, or later Bell operating companies (BOCs).
In 1899, American Telephone & Telegraph (AT&T) acquired the assets of its parent, the American Bell Telephone Company.
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Dans le réseau téléphonique commuté, un commutateur téléphonique met en relation deux correspondants suivant des règles fondées sur le numéro composé par l'appelant. Plusieurs commutateurs peuvent s'enchaîner entre l'appelant et le destinataire. Le choix d'un canal sur un équipement périphérique destinataire d'un appel s'appelle la sélection. La sélection suit des règles d'acheminement qui sont programmées dans chaque commutateur. Un circuit s'établit de proche en proche entre l'appelant et l'appelé.
AT&T Teleholdings, Inc., formerly known as Ameritech Corporation (and before that American Information Technologies Corporation), is an American telecommunications company that arose out of the 1984 AT&T divestiture. Ameritech was one of the seven Regional Bell Operating Companies that was created following the breakup of the Bell System. Ameritech was acquired in 1999 by SBC Communications, which subsequently acquired AT&T Corporation in 2006, becoming the present-day AT&T.
La scission du système Bell a été ordonnée le par un consentement convenu prévoyant qu'AT&T Corporation renoncerait, comme l'avait initialement proposé AT&T, au contrôle des compagnies exploitantes de Bell qui fournissaient le service téléphonique local aux États-Unis et au Canada jusqu'à cette date. Celle-ci a effectivement mis fin au monopole du système de Bell et l'a scindé en des sociétés distinctes qui continueront de fournir des services téléphoniques.
Information is processed in physical devices. In the quantum regime the concept of classical bit is replaced by the quantum bit. We introduce quantum principles, and then quantum communications, key d