Bell System

AT&T Inc., an abbreviation of its predecessor's original name, the American Telephone and Telegraph Company, is an American multinational telecommunications conglomerate headquartered at the Whitacre Tower in Downtown Dallas, Texas. AT&T is the world’s third-largest telecommunications company by revenue, the third largest wireless carrier in the United States behind T-Mobile and Verizon, and the nation's biggest fiber internet provider. On the New York Stock Exchange, AT&T trades under the ticker symbol “T,” and has a market capitalization of $186.83 billion. On the Fortune 500 (2025) AT&T ran

research and scientific development company

Verizon Communications Inc. ( ) is an American telecommunications company headquartered in New York City. It is the world's second-largest telecommunications company by revenue and its mobile network is the largest wireless carrier in the United States, with 146.1 million subscribers as of June 30, 2025.

Nortel Networks Corporation, formerly Northern Telecom Limited, was a Canadian multinational telecommunications and data networking equipment manufacturer headquartered in Ottawa, Ontario. It was founded in Montreal, Quebec, in 1895 as the Northern Electric and Manufacturing Company, or simply Northern Electric. Until an antitrust settlement in 1949, Northern Electric was owned mostly by Bell Canada and the Western Electric Company of the Bell System, producing large volumes of telecommunications equipment based on licensed Western Electric designs.

Canadian telecommunications and media company

engineering and manufacturing company

subsidiary of AT&T that provides voice, video, data, and Internet telecommunications

BellSouth, LLC (stylized as BELLSOUTH and formerly known as BellSouth Corporation) was an American telecommunications holding company based in Atlanta, Georgia. BellSouth was one of the seven original Regional Bell Operating Companies after the U.S. Department of Justice forced the American Telephone & Telegraph Company to divest itself of its regional telephone companies on January 1, 1984.

American telecommunications firm

telephone service provider

Bell Canada Enterprises

U.S. regional monopoly telephone companies created by 1984 AT&T breakup

Factory complex in Cicero, Illinois

former Bell Operating Company serving the Southeastern United States

thumb|Corporate HQ, 1095 Avenue of the Americas NYNEX Corporation () was an American telephone company that served five states of New England (Maine, Massachusetts, New Hampshire, Rhode Island and Vermont) as well as most of the state of New York from January 1, 1984, to August 14, 1997.

company that provides telephone service in California