The earliest cable systems were built in the late 1940's to bring clear broadcast television signals to remote or mountainous communities. The purpose was not to replace broadcast television but to enhance it. See United States v. Southwestern Cable Co., 392 U. S. 157, 161-164 (1968); D. Brenner, M. Price, & M. Meyerson, Cable Television and Other Nonbroadcast Video § 1.02 (1992); M. Hamburg, All About Cable, ch. 1 (1979). Modern cable systems do much more than enhance the reception of nearby broadcast television stations. With the capacity to carry dozens of channels and import distant programming signals via satellite or microwave relay, ...