Dead air, also known asunmodulated carrier,[citation needed] is an unintended period of silence that interrupts abroadcast during which no audio or video program material is transmitted.[1]
Dead air occurs inradio broadcasting when no audio program is transmitted for an extended period of time, usually more than a few seconds. Intelevision broadcasting, the term denotes the absence of both audio and video program material. However, acarrier wave is still transmitting. In radio, the result is silence, and in television, the result is a silent black or gray screen.[2][3][1]
Television directors may use the command "fade to black" or "to black" to indicate a momentary transition to a completely black image.[4] However, the term "dead air" is most often used in cases where program material comes to an unexpected halt, either through operator error or technical malfunction. Among professional broadcasters, dead air is considered one of the worst things that can occur.[5] Moreover, dead air may impact advertising revenue if it affects the airplay of paid commercials.[6]
The term "dead air" does not refer to a broadcasttransmitter that is intentionally shut down, i.e. "closed", "signed off" or "off the air", by a control operator. Such a broadcast transmitter is said to have gone "dark".[7][8]
Broadcast stations can use programmable devices known as "silence sensors", "off air alarms" or "silence monitors" that will sound an alarm and alert personnel if dead air persists more than a few seconds.[9][7]
In the U.S., prolonged dead air, such as a shutdown occurring without permission, is an actionable offense that can result in fines from theFederal Communications Commission (FCC). According to the FCC, a station has a 30-day limit for going silent without approval.[10][11]
On September 11, 1987,Dan Rather walked off the set of theCBS Evening News when a late runningU.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.[12] CBS affiliates criticized Rather for the incident.[13]
One significant case of dead air occurred duringSuper Bowl LII in 2018, when theNBC television broadcast experienced 26 seconds of dead air during a commercial break. The network blamed "a brief equipment failure."[14] NBC reported that no commercial advertising was lost.[6] Prior toSuper Bowl XLV,Green Bay, Wisconsin, radio stationWCHK-FM announced that it would intentionally go to dead air during the game, since the hometownPackers were playing in the game and station management believed nobody would be listening to music while the Super Bowl was being broadcast on another station.[15]
Many broadcasters install a silence detector independently operating from their broadcasting headquarters.In the event of dead air lasting more than an acceptable duration, e.g. ≤ −70 dB and (if applicable) static/no picture for 30 seconds, an emergency program is cued.[citation needed]
The emergency program contains at least some generic audio (and video) with astation identification.Radio stations usually play a loop of music.The playlist is fixed so staff listening in to their own station can recognize the pattern of titles, infer how long the outage has already (at least) lasted and take action to fix the problem.[citation needed]
Apart from providing a safeguard in the event ofunscheduled interruption (like a fire in the building or technical issues), this mechanism may be useddeliberately during programmed blackouts caused by strikes of technicians, journalists, and producers.When staff of the French public broadcasting networkRadio France went on strike in September 2020, a pretaped message informing listeners that no service is available due to industrial action was inserted into the loop.[16]