The term has taken  a different  meaning  during  various periods in broadcasting. Initially, the term  was  applied to the simultaneous transmission of important events over two or more  radio outlets.  Later,  it  referred to the simultaneous transmission of programs on radio and television. This occurred during the 1960s, when some of the most popular radio programs became television programs but the audio portion was still simulcast on radio . This practice was short-lived, however, as the number of homes with TV sets increased and radio shifted increasingly to music-based programming. The very slow growth in FM radio during the 1950s and 1960s was due, in part, to the simulcasting of radio programming over co-owned AM and  FM stations. In 1964, the Federal Communications Commission (FCC) acted to force the independence of FM stations by severely restricting the number of hours that AM and FM stations could simulcast during any given broadcast day. although protests by radio station owners delayed implementation of the rule until January 1, 1967. (Ironically. the FCC removed the restrictions on AM/FM simulcasting a quarter of a century later so that struggling AM stations could simulcast the programming of their stronger FM sister stations.)

     Simulcasting of musically oriented programs by television and FM stations occurred on an occasional basis during the 1970s and 1980s. Sometimes these programs included opera or other classical presentations: on other occasions, rock concerts were simulcast. The improved sound fidelity and stereo capability of newer television sets have diminished the need for such audio-enhancement simulcasting. although some TV/FM simulcasting still occurs.

     The terrorist attacks on the World Trade Center in New York City and the Pentagon in Washington. D.C.. on September 11, 2001, created a very different need for simulcasting. Immediately following these attacks. broadcast and cable networks simulcast their news coverage on co-owned cable networks that did not ordinarily carry news. ABC News was carried on the Entertainment and Sports Programming Network (ESPN): CBS covered the music networks Video Hits I (VH I) and. later in the day. Music Television (MTV): and CNN News was simulcast on both Turner Network Television (TNT) and the Turner Broadcasting System (TBS).

     On a lighter note. simulcasting has even been used to carry two slightly different versions of the same program. When ESPN cablecast the film Season On the Brink (2002) about former Indiana University basketball coach Bobby Knight. The same movie was simulcast-but with the raw language and obscenities bleeped-on ESPN2.

     Currently, the term "simulcasting" is most relevant to the development and adaptation of digital television. Both broadcasters and regulators recognize that newer. more advanced forms of television transmission will have to be phased in gradually since viewers with standard television receivers are not willing to accept the immediate obsolescence of their  current TV sets.

     As of 2002. Many television stations in larger markets are simulcasting on two separate signals. A standard (NTSC analog) signal is broadcast over the television station's basic channel. while a second ATSC digital signal is transmitted over a separate channel allocated to that station specifically for this purpose by the FCC.

     Initially, the FCC suggested that this simulcasting would continue until 2006. at which time 85 percent of U.S. households would be able to receive a digital signal. Simulcasting would then be discontinued, and the analog channels would be returned to the FCC for alternative use. As of 2002. That time frame seems very much in doubt, and observers speculate that analog/ digital simulcasting will continue long past the 2006 date.

     In addition to the simulcasting of analog and digital signals. The traditional simulcasting of major events by one or more television and/or cable outlets is a well­ established practice and one not likely to end in the near term.