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Dead air is defined as "a period of silence especially during a radio broadcast," which has been extended, in some formal definitions, to include both audio and video signals (and so to this extent, to television as well as radio broadcasts). Hence, generalizing, the term can be understood to refer to any unintended period of silence interrupting any media broadcast, during which no signal, audio or video, is transmitted.〔 Technically, the absence of sound in a radio transmission implies that only an unmodulated carrier wave is being transmitted, for modes that send one, or absence of the transmitting signal altogether for modes that do not. The term is most often used in cases where program material comes to an unexpected halt, either through operator error or for technical reasons. Among professional broadcasters, dead air is considered one of the worst things that can occur. Moreover, having dead air during commercial segments or sponsor announcements can cost networks considerable revenue. As noted, the term "dead air" is also sometimes used in television broadcasting, generally when a television channel has an interruption to its output, resulting in a blank screen or in the case of digital television, a frozen image, until output is restored or an apology message is broadcast. Some television stations also use the related phrases "in black" and "going to black" for transmitting an unmodulated carrier, meaning both a completely black image and a completely silent audio stream are sent; other stations limit the term "in black" to loss of video where audio continues normally, and "dead air" is used for sending an unmodulated carrier signal. However, the terms "dead air" and "in black" are not used when a station is broadcasting no signal whatsoever, even a carrier wave, which is called "going off-the-air." ==Examples== An example of dead air was a Chris Evans radio transmission for the British Virgin Radio (now known as Absolute Radio) station. As a promotional stunt, Evans did not arrive for work, and his show went to air carrying nothing for about 25 minutes. Another case was BBC Radio 4's failure to broadcast Big Ben's midnight chimes on New Year's Day 2003; after the chimes were announced, a technical error caused the station to fall silent for a minute. This was caused by the correct feed not being faded up. The chimes were supposed to be coming via a new link which the BBC had installed to Westminster to avoid dead air. On September 11, 1987, Dan Rather walked off the set of the CBS Evening News when a late running U.S. Open tennis match threatened to delay the start of his news broadcast. The match then ended sooner than expected but Rather was gone. The network broadcast six minutes of dead air before Rather was found and returned to the studio. There was considerable criticism of Rather for the incident. One significant case of dead air during a Super Bowl was during Super Bowl XLV in 2011, when WCHK-FM, a station in the Green Bay, Wisconsin area, announced it would counterprogram the game with dead air, since the hometown Packers were in the game. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dead air」の詳細全文を読む スポンサード リンク
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