Emergency Alert System

Encyclopedia : E : EM : EME : Emergency Alert System

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 Digital Broadcast Satellite will be required to participate beginning May 31, 2007. Video Dial Tone (OVS) will be required to participate beginning July 1, 2007.

Contents

1 Technical concept
2 EAS for consumers
3 Incidents
4 See also
5 External links

Technical concept

In the EAS system, messages are originated in four parts. The first part is the SAME header code, the most critical part of the EAS design. It is repeated three times, so that decoders can pick "best two out of three" for each byte, thereby eliminating most errors which can cause an activation to fail. The header code contains information about who originated the alert (President, state or local authorities, the National Weather Service, or the broadcaster), what the event is (tornado, flood, nuclear), the areas affected (up to 32 counties or states), how long the alert is valid for, the exact UTC time it was issued, and the identification of the station or other entity. (See SAME for a complete breakdown of the header.)

Each station must have installed an EAS decoder which then interprets these data bursts. They make three harsh sounding tones that DJs sometimes refer to as "duck farts". Two of the three bursts must be found to be identical by the decoder for the message to be valid. The decoder then decides, based on its pre-programming, whether to ignore the message as not pertaining to the local area, or whether to relay it on the air. The FCC requires all broadcast stations relay EAN and EAT messages immediately, and all required weekly and monthly tests (RWT and RMT) within 60 (formerly 15) minutes. Stations may also choose to relay other alerts such as severe weather and AMBER Alerts. For reliability, every station must monitor at least two other source stations, one of which must be designated a local primary.

The SAME header bursts are followed by an alert tone, lasting between eight and 25 seconds depending on the originating station, that carries no information. The tone, a combination of 853 Hz and 960 Hz sine wave tones, is the same combination of two tones that the old Emergency Broadcast System used as its attention signal. Like the old EBS, this tone is in turn followed by a voice message giving details of the alert.

The message is ended by three bursts of the AFSK "EOM", or end of message, which is the text NNNN, preceded each time by the binary 10101011 calibration.

All EAS equipment must be tested weekly. The RWT, or required weekly test, consists only of the three AFSK header bursts and the three AFSK EOM bursts with no voice, and are essentially internal tests of the system components. Required monthly tests (RMT) are transmitted with all four parts, with the voice (and text on TV) stating that it is only a test. The RMT must be transmitted in the daytime and at night in alternating months.

The number of events in the national system has recently grown by several increments, and is now forty-nine events. At first, they were almost all weather events with only one to three possible categories for civil emergencies, but several classes of non-weather emergencies have now been added. In most states, the AMBER Alert System, for child abduction emergencies, has now been added as well.

Stations are required by law to keep full logs of all received and transmitted EAS messages, usually accomplished by a small receipt printer in the endec unit. Logs may also be kept electronically inside the unit, as long as there is access to an external printer, sometimes via transfer to a personal computer.

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.

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, Best Buy,Ham Radio Outlet,Amateur Electronic Supply,Delaware Amateur Radio Supply, and several others. Other specialty receivers for AM/FM/ACSSB(R)(LM(R)) radio 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

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.

External links

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