formerly American Telephone and Telegraph Co.
U.S. telecommunications corporation.
It was established as a subsidiary of Bell Telephone Co. (founded by Telstar satellite communications system. Years of federal antitrust litigation resulted in AT&T's 1984 divestment of its 22 regional telephone companies, which were combined to form seven "Baby Bells": Nynex, Bell Atlantic, Ameritech, BellSouth, Southwestern Bell Corp., US West, and Pacific Telesis Group. Many have since merged. In 1996 AT&T divided its operations into three separate companies: AT&T Corp., Lucent Technologies Inc. (composed of the former operations of Western Electric and {{link=Bell Laboratories">Bell Laboratories ), and the NCR Corp. AT&T was divided into four units in 2000.