Emergency Alert System
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- This article refers to the Emergency Alert System. For other uses of the term EAS please see EAS.
The Emergency Alert System (EAS), is a national system in the U.S. put into place in 1994, superseding the Emergency Broadcast System and is jointly administered by the Federal Communications Commission (FCC), FEMA, and the National Weather Service. The official EAS system is designed to enable the President of the United States to speak to the United States within 10 minutes (this official federal EAS system has never been activated). Voluntary EAS systems at the state and local level also exist. The EAS covers both AM/FM/ACSSB(R)(LM(R)) radio and VHF Low/VHF Medium/VHF High/UHF/television (including low-power stations),HRC/IRC/STD/EIA cable television and wireless cable television companies. Digital television, digital cable, XM Satellite Radio, Sirius Satellite Radio, Grendade, Worldspace, IBOC, DAB and digital radio broadcasters will be required to participate in EAS beginning December 31, 2006. DIRECTV, Dish Network, and any other Direct Broadcast Satellite providers will be required to participate beginning May 31, 2007. Video Dial Tone (OVS) will be required to participate beginning July 1, 2007.
Listen to:
A SAME header
An attention signal
A full EAS transmission
Contents |
[edit] Technical concept
The SAME header is most critical part of the EAS design. It contains information about who originated the alert (the President, state or local authorities, the National Weather Service, or the broadcaster), a short, general description of the event (tornado, flood, severe thunderstorm), the areas affected (up to 32 counties or states), the expected duration of the event (in minutes), the date and time it was issued (in UTC), and an identification of the originating station. (See SAME for a complete breakdown of the header.)
30+ radio stations are designated as National Primary Stations in the Primary Entry Point System to distribute Presidential messages to other broadcast stations and cable systems (Moore 6).
Because the header lacks error detection codes it is repeated three times for redundancy. EAS decoders compare the received headers against one another, looking for an exact match between any two, eliminating most errors which can cause an activation to fail. The decoder then decides whether to ignore the message or whether to relay it on the air based on whether the message applies to the local area served by the station (which is pre-programmed into the decoder).
The SAME header bursts are followed by an attention signal which lasts between eight and 25 seconds, depending on the originating station. The tone consists of a combination of 853 Hz and 960 Hz sine waves and is the same attention signal used by the older Emergency Broadcast System. Like the EBS, the attention signal is followed by a voice message describing the details of the alert.
The message ends with three bursts of the AFSK "EOM", or End of Message, which is the text NNNN, preceded each time by the binary 10101011 calibration.
[edit] Station requirements
The FCC requires all broadcast stations to install and maintain EAS decoders and encoders at their control points. These decoders continuously monitor the signals from other nearby broadcast stations for EAS messages. For reliability, at least two other source stations must be monitored, one of which must be a designated local primary.
Upon reception of an alert, a station must relay EAN (Emergency Action Notification) and EAT (Emergency Action Termination) messages immediately (US FCC 7), and all required weekly and monthly tests (RWT and RMT) within 60 minutes (formerly 15). Stations may optionally relay other alerts such as severe weather and child abduction emergencies (AMBER Alerts).
All EAS equipment must be tested weekly. The required weekly test (RWT) consists of the header and the end-of-message SAME bursts. On TV, a graphic explaining that it is a test is required, but a voice announcement is not necessary. Some stations do it anyway. KMBC-TV in Kansas City says, "This is a test of the Emergency Alert System"; after the SAME signals are transmitted, the announcer says, "This has been a test of the Emergency Alert System."
Radio stations are required to announce, "This is a test of the Emergency Alert System" before activating the SAME signals.
Required monthly tests (RMT) consist of all four message parts (header, alert tone, voice announcement, end-of-message marker). The voice message runs something like this:
"This is a test of the Emergency Alert System. If this had been an actual emergency such as severe weather watches or warnings or other local area emergencies, following the tone you just heard would have been information about the nature of the emergency and safety instructions for the protection of life and property. Tests of the system are conducted monthly in accordance with FCC regulations. This has been a test of the Emergency Alert System. We now resume normal programming."
The RMT is scheduled such that it alternates between daytime and nighttime each succeeding month.
Stations are required by law to keep full logs of all received and transmitted EAS messages. Logs may be kept by hand but are usually kept automatically by a small receipt printer in the encoder/decoder unit. Logs may also be kept electronically inside the unit as long as there is access to an external printer or method to transfer them to a personal computer.
[edit] Additions and proposals
The number of event types in the national system has grown to forty-nine. At first, almost all but three of the events were weather-related, the remaining types dedicated for civil emergencies. Since then, several classes of non-weather emergencies have been added, including, in most states, the AMBER Alert System for child abduction emergencies.
In 2004, the FCC issued a Notice of Proposed Rulemaking seeking comment on whether EAS in its present form is the most effective mechanism for warning the American public of an emergency and, if not, on how EAS can be improved.
[edit] EAS for consumers
EAS is designed to be useful for the entire public, not just those with SAME-capable equipment. However, several consumer-level radios do exist, especially weather radio receivers, which are available to the public through both mail-order and retailers like Radio Shack, Circuit City, and several others. Other specialty receivers for AM/FM/ACSSB(R)(LM(R)) are available only through mail-order, or in some places from federal, state, or local governments, especially where there is a potential hazard nearby such as a nuclear plant or chemical factory. These radios come pre-tuned to a station in each area that has agreed to provide this service to local emergency management officials and agencies, often with a direct link back to the plant's safety system or control room for instant activation should an evacuation or other emergency arise.
The ability to narrow messages down so that only the actual area in danger is alerted is extremely helpful in preventing false warnings, which was previously a major tune-out factor. Instead of sounding for all warnings within a station's area, SAME-decoder radios now sound only for the counties they are programmed for. When the alarm sounds, anyone with the radio knows that the danger is nearby and protective action should be taken. For this reason, the goal of the National Weather Service is that each home should have both a smoke detector and a SAME weatheradio.
A private website called the Emergency Email Network offers to send an email or SMS text message to registered users in the event of an EAS activation. Some desktop weather monitoring programs, such as WeatherBug, offer a computer alert during emergencies.
Currently under development is new infrastructure called the Digital Emergency Alert System. This system would allow the transmission of emergency alerts directly to citizens and responders without the need for a special receiver. These alerts would be sent to users of computers, mobile phones, pagers, and other devices.
See also: NAVTEX
[edit] Incidents
Several state officials including New York Governor George Pataki, former New York City Mayor Rudolph W. Giuliani and U.S. Congressmen and Senators have questioned members of the FCC on why the Emergency Alert System was not implemented nationwide on radio and television stations during the September 11, 2001 Terrorist Attacks where official government information is/was supposed to be distributed in place of local/network programming or newscasts. The EAS was to have issued such messages that the United States was under attack, but no warning broadcast was issued, even in New York City.
On February 1, 2005 at 2:10 pm Eastern Standard Time an employee within the Connecticut Office of Emergency Management inadvertently activated an EAS message over radio and television stations telling residents to evacuate the state immediately. At 3:45 pm officials at the OEM announced that the activation and broadcast of the Emergency Alert System was in error due to the fact that the button used to conduct weekly EAS tests is located next to a button that is used to issue an emergency alert to evacuate the state. In addition to questioning how the mistake happened, some concern was raised at the fact that almost no one seemed to take the evacuation order seriously, even before it was rescinded.
[edit] Works Cited
- Moore, Linda K. United States. Congressional Research Service. Emergency Communications: The Emergency Alert System (EAS) and All-Hazard Warnings. Congressional Research Service, 2006. Federation of American Scientists. 20 Nov. 2006 http://www.fas.org/sgp/crs/homesec/RL32527.pdf.
- United States. Federal Communications Commission. Emergency Alert System 2001 AM & FM Handbook. 2001.
[edit] See also
- Media:Emergency alert system tone.ogg
- NOAA Weather Radio All Hazards
- Emergency population warning
- 911 broadcast
