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The Emergency Alert System (EAS) is a national warning system in the United Statesmarker put into place in 1997, superseding the Emergency Broadcast System (EBS) and the CONELRAD System and is jointly coordinated by the Federal Communications Commission (FCC), Federal Emergency Management Agency (FEMA), and the National Weather Service (NWS). The official EAS is designed to enable the President of the United States to speak to the United States within 10 minutes (this official federal EAS has never been activated). The EAS regulations and standards are governed by the Public Safety and Homeland Security Bureau of the FCC. Each State and several territories have their own EAS plan.

The EAS covers both AM, FM and ACSSB(R)(LM(R)) radio, and VHF, UHF and cable television including low-power stations. Digital television and cable providers, along with XM and Sirius satellite radio, Worldspace, IBOC, DAB and digital radio broadcasters have been required to participate in the EAS since December 31, 2006. DIRECTV, Dish Network, Muzak, DMX Music, Music Choice and all other DBS providers have been required to participate since May 31, 2007. Video Dial Tone (OVS) has been required to participate since July 1, 2007.

Technical concept

Messages in the EAS are composed of four parts: a digitally encoded SAME header, an attention signal, an audio announcement, and a digitally encoded end-of-message marker.
A Sage EAS ENDEC unit.

The is the 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 (PEP) System to distribute Presidential messages to other broadcast stations and cable systems. The Emergency Action Notification is the notice to broadcasters that the President of the United States or his designee will deliver a message over the EAS via the PEP system. "You {AM and FM broadcasters} will hear the following Emergency Action NotificationMessage from the EAS decoder. This is an Emergency Action Notification requested by the White House. All broadcast stations will follow activation procedures in the EAS Operating Handbook for a nationallevel emergency. The President of the United States or his representative will shortly deliver a message over the Emergency Alert System."

Communications links

The FEMA National Radio System (FNARS) "Provides Primary Entry Point service to the EmergencyAlert System," acts as an emergency presidential link into the EAS, and is capable of phone patches. The FNARS net control station is located at the Mount Weather Emergency Operations Centermarker.

What the national level EAS would not do

In a New York Times article (correction printed January 3, 2002) the lack of news coverage by station WNYCmarker FM, New York, was explained by the destruction of its broadcast transmitters with the collapse of the World Trade Centermarker north tower on 9/11. "No president has ever used the current [EAS] system or its technical predecessors in the last 50 years, despite the Soviet missile crisis, a presidential assassination, the Oklahoma City bombingmarker, major earthquakes and three recent high-alert terrorist warnings.... Michael K. Powell, chairman of the Federal Communications Commission, which oversees the Emergency Alert System, pointed to 'the ubiquitous media environment,' arguing that the system was, in effect, scooped by CNN, MSNBC, Fox News and other channels.... [FEMA] activates the alert system nationally at the behest of the White House on 34 50,000-watt stations that reach 98 percent of Americans.... Beyond that, the current Emergency Alert System signal is an audio message only—which pre-empts all programming—so that viewers who were watching color images of the trade center on Sept. 11 would have been able to see only a blank screen along with a presidential voice-over, if an emergency message had been activated."

Other than the on-screen scrolling message accompanying the initial activation, the Federal Communications System EAS TV Handbook - 2007 does not include any sort of visual element. Under the SAME protocol, precise emergency information would be delivered aurally.

EAS header

Because the header lacks error detection codes it is repeated three times for redundancy. However, the repetition of the data can itself be considered an error detection and correction code—like any error detection or correction code, it adds redundant information to the signal in order to make errors identifiable. 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 to relay it on the air if the message applies to the local area served by the station (following parameters set by the broadcaster).

The SAME header bursts are followed by an which lasts between eight and 25 seconds, depending on the originating station. The tone is on a NOAA Weather Radio station, while on commercial broadcast stations, it consists of a "two tone" combination of 853 Hz and 960 Hz sine waves and is the same attention signal used by the older Emergency Broadcast System. The "two tone" system is no longer required as of 1998 and is to be used only for audio alerts before EAS messages. 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.

The White House has endorsed the migration to the Common Alerting Protocol and FEMA is in the process of testing implementation.

Could the EAS function in a national emergency?

The 2007 FCC EAS Handbooks leave doubts about the ability of EAS to deliver a presidential message in an extreme national crisis. An ENDEC is a device (pictured above) used by broadcasters to retransmit the EAS header of an EAN received by PEP stations or other sources. The header and attention signal is followed by an audio feed provided by the White House to the PEP stations. A number of minutes after an EAN is broadcast by PEP stations, the audio feed will carry the presidential message. Stations use the ENDEC to relay this audio.

The operational design of some equipment, such as that made by SAGE, runs contrary to FCC handbook instructions. The ENDEC is programmed by the manufacturer to generate an EAN header and attention signal immediately upon receipt of an EAN. The unit will also put on the air audio from whatever source the EAN was received (a Primary Entry Point station, for example). FCC handbooks (see pages 9 and 10) instruct all AM and FM stations to transmit announcements between the release of an EAN by the White House and the audio of a presidential message, even if the automatic mode of their ENDEC is programmed to disallow such announcments. The SAGE ENDEC, while equipped with both an abort and time delay feature, has both of these disabled during an EAN.

Simply stated, at least some equipment does not appear to have any override capability for the purpose of reading FCC announcements. Audio from PEP stations, whatever its content, will be aired by any station receiving it—by default automatically.

News reports from an accidental EAN in 2007 illustrate the problem. "About 7:35 a.m. Good Morning America was about to do some weather when the tones came. And then a message on red background saying, 'The emergency action notification network has issued an emergency action notification for the United States....' After some dead air, WGN radio morning host Spike O'Dell is suddenly being heard on just about every radio and TV station in Chicago, and he's not sure of what's happening.... When the state's emergency alert system is activated WGN-AM is the station designated to simulcast the message. Tuesday's was an emergency action notification."

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. Stations are to retain the latest version of the EAS handbook.

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.

In addition to the audio messages transmitted by radio stations, television stations must also transmit a visual message. A text "crawl" is displayed at the top of the screen. A color coded "crawl" system is often used where the color signifies the priority of the message. Some television stations transmit only the visual message which is outside of the requirements. A television station may be used for monitoring by another station and thus the audio is necessary.

Upon reception of an alert, a station must relay EAN (Emergency Action Notification) and EAT (Emergency Action Termination) messages immediately (US FCC 7). Stations traditionally have been allowed to opt out of relaying other alerts such as severe weather, and child abduction emergencies (AMBER Alerts) if they so choose. Under new rules published on July 12, 2007, the FCC intends to require all stations to relay state and local alerts that are approved by their states' governors (pending approval of the CAP standard).

Some stations may be non-participating, and do not relay messages. Instead they transmit a message instructing listeners/viewers to tune to another station for the information, and they must then suspend their operation.

FCC equipment certification

EAS equipment must be FCC certified for use as described above. The following companies have been certified by the FCC to manufacture such equipment.

Companies certified to manufacture encoder/decoder units
Company Name FCC ID
Burk Technology Inc. MPEEAS
Cadco Systems, Inc. ND2EAS
Digital Alert Systems, LLC R8VDASDEC-1EN
Gorman-Redlich Manufacturing Co. MVZEAS1
Hollyanne Corp. GRQMIP-921
M&N Electronics LLC M46HU-961
Multi-Technical Services, Inc. HTG3000D
Sage Alerting Systems, Inc. MAX1822
Trilithic, Inc. P4V-EASYPLUS-1

Companies certified to manufacture decoder-only units
Company Name FCC ID
Digital Alert Systems, LLC R8VDASDEC-1EN
Gorman-Redlich Manufacturing Co. MVZEAS1
Trilithic, Inc. P4V-EASYPLUS-1

System test

All EAS equipment must be tested weekly. The required weekly test (RWT) consists of the header and the end-of-message SAME bursts. The RWT does not need an audio or graphic message announcing the test, although many stations will provide them as a courtesy to the listener or viewer. Television stations are not required to transmit a video message for weekly tests. RWTs are scheduled by the station, alternating between night and day, and are not relayed.

On cable systems before the start of the EAS test, all of a system's channels, both on cable ready televisions directly connected to the coaxial cable, and those on cable boxes, are redirected to one digital channel which is received on all tiers of service, but doesn't usually give out news or weather information (such as the TV Guide Network, QVC, HSN, or a public access station), where the test occurs from the local headend office or from the system's master office elsewhere in the region. Newer technology allows cable DVR and video on demand systems to interrupt playback of a program for an EAS test. After the test ends, the one channel usually remains on screen for 5-10 additional seconds before the original station/network is returned to.

Required Monthly Tests (RMTs) are generally originated by the primary relay station or a State's EAS agency, relayed by broadcast and cable stations. RMTs are conducted with the following procedure:
  1. Normal programming is suspended (commonly during commercial breaks), and an announcement may be made such as: "The following is a monthly test of the Emergency Alert System. This is only a test."
  2. The SAME Header burst is sent, perhaps followed by an attention signal.
  3. Another voice message is sent, which runs something like this:
  4. :"This is a coordinated monthly test of the broadcast stations in your area. Equipment that can quickly warn you during emergencies is being tested. If this had been an actual emergency such as a tornado warning or severe thunderstorm warning, official messages would have followed the alert tone. This concludes this test of the Emergency Alert System."
  5. The SAME EOM burst is sent.
RMTs must be performed between 8:30 a.m. and local sunset during odd numbered months, and local sunset to 8:30AM for even months. Received tests must be retransmitted within 60 minutes from receipt. Additionally, an RMT cannot be scheduled or conducted during an event of great importance such as a pre-announced Presidential speech, coverage of a national election or a major sporting event such as the Olympic Games, the Super Bowl or the World Series as mentioned in individual EAS state plans.

An RWT is not required during a calendar week in which an RMT is scheduled. No testing has to be done at all during a calendar week in which the EAS has been legitimately activated. Coordinated national tests are conducted at least once every year and are very similar to RMTs Part 1 of a two part Youtube video of part of a national EAS test on Dish Network />. Part 2 of a two part Youtube video of part of a national EAS test on Dish Network />.

Additions and proposals

The number of event types in the national system has grown to eighty. At first, almost all but three of the events (civil emergency message, immediate evacuation, and emergency action notification (national emergency)) were weather-related (such as a tornado warning), 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. As noted above, rules implemented by the FCC on July 12, 2007 provisionally endorse replacing the SAME protocol with CAP and allow governors to compel universal activation of the system within their own states.

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 including Radio Shack 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 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 weather radio.

The United States Military has recently employed emergency notification technologies at The United States Academy at West Point, The United States Air Force Academy and numerous military installations to assist in critical and mass notification to base personnel using alert software designed by Desktop Alert.

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. These alerts would be sent to users of computers, mobile phones, pagers, and other devices.


  • During the September 11 attacks in 2001, "... the EAS was not activated nationally or regionally in New York or Washington during the terrorist attacks on the nation." Richard Rudman, then chairman of the EAS National Advisory Committee explained that near immediate coverage in the national media meant that the media itself provided the warning or alert of what had happened and what might happen as quickly as the information could be distributed. "Some events really do serve as their own alerts and warnings. With the immediate live media coverage, the need for an EAS warning was lessened." 34 PEP stations were kept on high alert for use if the President had decided to order an Emergency Action Notification. "PEP is really a last-ditch effort to get a message out if the president cannot get to the media." Stine, Randy J. "Terrorism Attacks Cue EAS Debate." RWonline, Radio World Newspaper. 26 Sep. 2001. IMAS Publishing (USA) Inc. 7 Apr. 2007 />.

  • On February 1, 2005 someone inadvertently activated an EAS message over radio and television stations in Connecticut telling residents to evacuate the state immediately. Officials at the Office of Emergency Management announced that the activation and broadcast of the Emergency Alert System was in error due to possibly the wrong button being pressed. "State police said they received no calls related to the erroneous alert."

  • On June 26, 2007, the EAS in Illinoismarker was activated at 7:35AM CDT and issued an Emergency Action Notification Message for the United States. This was followed by dead air and then WGN-AMmarker (720) radio (the station designated to simulcast the alert message) being played on almost every television and radio station in the Chicagomarker area and throughout much of Illinois . The accidental EAN activation was caused when a government contractor installing a new satellite receiver as part of a new national delivery path incorrectly left the receiver connected and wired to the state EOC's EAS transmitter before final closed circuit testing of the new delivery path had been completed.

EAS event codes

In popular culture

In the video game Call of Duty: Modern Warfare 2, during a Russianmarker invasion of the United Statesmarker, one of the loading screen videos is simply the Emergency Alert System. A message scrolls across the screen giving evacuation instructions for residents of Prince George's Countymarker.

See also


  1. Emergency Alert System
  2. Moore, Linda K. United States. Congressional Research Service. Emergency Communications: The Emergency Alert System (EAS) and All-Hazard Warnings. p. 6 Congressional Research Service, 2006. Federation of American Scientists. 20 Nov. 2006
  3. United States Code of Federal Regulations
  4. Common Alerting Protocol, Cybertelecom
  5. Presidential Initiative related to CAP
  6., FCC Certified EAS equipment vendors.
  7. - Emergency Alert System Activated By Mistake

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