The network has its origins in United Independent Broadcasters Inc., a collection of 16 radio stations that was purchased by Paley in 1928 and renamed the Columbia Broadcasting System. Under Paley's guidance, CBS would first become one of the largest radio networks in the United States, and eventually one of the Big Three American broadcast television networks. In 1974, CBS dropped its former full name and became known simply as CBS, Inc. The Westinghouse Electric Corporation acquired the network in 1995, renamed its corporate entity to the current CBS Broadcasting, Inc. in 1997, and eventually adopted the name of the company it had acquired to become CBS Corporation. In 2000, CBS came under the control of Viacom, which was formed as a spin-off of CBS in 1971. In late 2005, Viacom split itself into two separate companies and re-established CBS Corporation – through the spin-off of its broadcast television, radio, and select cable television and non-broadcasting assets – with the CBS television network at its core. CBS Corporation is controlled by Sumner Redstone through National Amusements, which also controls the current Viacom.