Prior to Jan. 1, 1984, an aggregate term for AT&T encompassing 24 Bell operating companies providing local exchange phone service, the AT&T Long Lines Division providing long distance connections, an equipment manufacturing arm known as Western Electric, and a research and development arm known as Bell Laboratories. The Bell System was broken up by the AT&T divestiture.

The collection of companies headed by AT&T and consisting of the 22 Bell Operating Companies and the Western Electric Corporation. The Bell System was dismantled by divestiture on January 1, 1984.

A group of affiliated RBOC s (Regional Bell Operating Companies) in the USA which operate under consistent rules and specifications, many of which are set by AT&T.

A group of affiliated regional Bell operating companies (RBOCs) in the United States that operate under rules and specifications established primarily by AT&T and the FCC.

The Bell System was a trademark and service mark used by the U.S. telecommunications company American Telephone & Telegraph Company (AT&T) and its affiliated companies to co-brand their extensive circuit-switched telephone network and their affiliations with each other. The telephone system had a near-monopoly on the U.S. telephone market until its divestiture in 1984. The Bell System was commonly called by the nickname Ma Bell.