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AT&T Teleholdings, Inc., formerly known as Ameritech Corporation (and before that American Information Technologies Corporation), was a U.S. 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 by SBC Communications in 1999 which subsequently acquired AT&T Corporation in 2006, becoming the present-day AT&T Inc. ==Overview== Ameritech was created as a holding company; under its umbrella were: * Illinois Bell Telephone Company * Indiana Bell Telephone Company, Inc. * Michigan Bell Telephone Company * Ohio Bell Telephone Company * Wisconsin Bell, Inc. For Ameritech's first nine years, it maintained these Bell brands inherited from the Bell System—though public displays of the Bell companies' names were often captioned "An Ameritech Company". In January 1993, Ameritech officially retired the Bell brands and marketed itself with solely the Ameritech name across all five states in its territory. It added "d/b/a Ameritech (state)" to the names of its Bells to communicate brand unity. Ameritech also owned Ameritech Cellular, a wireless company that operated cellular networks in many of the major cities of these states. Ameritech Cellular was previously called Ameritech Mobile Communications. Ameritech Advanced Data Services (AADS,) Network Access Point (NAP,) was one of the original four, National Science Foundation exchange points in the United States starting in 1994. AADS was a Tier 1 network Internet Exchange Point in Chicago Illinois that provided service to higher education and research networks via a program called Star TAP and commercial networks. After the merger with SBC, AADS did business as the SBC Network Access Point or SBC/AADS NAP. Prior to its merger with SBC Communications, Ameritech's corporate headquarters were in a leased space above the Chicago Mercantile Exchange on floors 34 through 39 of 30 S Wacker Dr, Chicago. Further corporate offices were located at 225 W Randolph St, Chicago (formerly "The Illinois Bell Building") and 2000 W. Ameritech Center Drive, Hoffman Estates (Ill.) ("The Ameritech Center"). It was traded on the NYSE under the "AIT" symbol. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ameritech」の詳細全文を読む スポンサード リンク
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