Emergency Alert System - Wikipedia

Main article: Specific Area Message Encoding

Messages in the EAS are composed of four parts: a digitally encoded Specific Area Message Encoding (SAME) header, an attention signal, an audio announcement, and a digitally encoded end-of-message marker.

 

The SAME headerⓘ 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 (NOAA/NWS), 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.

There are 79 radio stations designated as National Primary Stations in the Primary Entry Point (PEP) System to distribute presidential messages to other broadcast stations and cable systems.[4]

The National Emergency Message (formerly known as the Emergency Action Notification) is the notice to broadcasters that the president of the United States or their designee will deliver a message over the EAS via the PEP system.[5] The government has stated that the system would allow a president to speak during a national emergency within 10 minutes.[6][7]

List of Primary Entry Point stations[8]

Operational area	Station	Citations
National	NPR, PRN, SXM
United States Virgin Islands	WSTA	[9]
Puerto Rico	WKAQ	[10]
Maine	WGAN	[11]
New Hampshire, Vermont, Massachusetts, Rhode Island	WBZ	[12][13][14][15]
Connecticut	WTIC	[16]
New York City, New Jersey	WABC	[17]
Northeast New York	WROW
South Central New York	WBNW-FM	[17]
North Central New York	WHEN
Western New York	WHAM	[17]
Delaware, Eastern Pennsylvania	WTEL, WHYY-FM	[18]
Western Pennsylvania	KDKA	[19]
West Virginia	WCHS	[20]
Maryland	WBAL	[21]
District of Columbia	WFED	[22]
Eastern Virginia	WTAR
Central Virginia	WRXL	[23]
Western Virginia	WPLY
Eastern North Carolina	WSFL-FM
Central North Carolina	WQDR-FM	[24]
Western North Carolina	WBT
Upstate South Carolina	WKVG
Downstate South Carolina	WCOS-FM	[25]
Georgia	WMAC, WSRV	[26]
North Florida	WOKV	[27]
Central Florida	WFLF	[27]
South Florida	WAQI	[27]
Alabama	WJOX	[28]
Mississippi	WMSI-FM
East Tennessee	WJCW, WJXB-FM	[29]
Middle Tennessee, Southwest Indiana	WSM	[29][30]
West Tennessee	WREC	[29]
Kentucky, Southwest Ohio, Southeast Indiana	WLW	[31][32]
Northeast Ohio	WTAM	[32]
Michigan	WJR	[33]
Northwest Indiana, Northern Illinois	WLS	[30][34]
Southern Illinois, Eastern Missouri	KMOX	[30][35]
Wisconsin	WTMJ	[36]
Minnesota	WCCO	[37]
Iowa	WHO	[38]
Central Missouri	KTXY
Western Missouri	WHB	[35]
Arkansas	KAAY
Southeast Louisiana	WWL	[39]
Northwest Louisiana	KWKH
Central Texas	KLBJ	[40]
North Texas	WBAP, KSCS	[40]
Southeast Texas	KTRH	[40]
West Texas	KROD	[40]
Oklahoma	KRMG, KOKC
Nebraska	KRVN	[41]
North Dakota, South Dakota (secondary)	KFYR	[42][43]
Montana	KERR	[44]
Wyoming	KTWO	[45]
Colorado, South Dakota (primary)	KOA	[43]
New Mexico	KKOB
Arizona	KFLT	[46]
Utah	KSL	[47]
Idaho	KBOI	[48]
Northern Nevada	KKOH
Southern Nevada	KXNT
San Diego area	KOGO	[49]
Southern California	KFI, KNX	[49]
Central California	KMJ	[49]
Northern California	KCBS	[49]
Hawaii	HEMA	[50]
American Samoa	WVUV-FM
Guam and Northern Marianas	KTWG
Oregon	KOPB-FM, KPNW	[51]
Washington	KIRO	[52]
Alaska	KFQD	[53]

Primary Entry Point stations

edit

The National Public Warning System, also known as the Primary Entry Point (PEP) stations, is a network of 77 radio stations that are, in coordination with FEMA, used to originate emergency alert and warning information to the public before, during, and after incidents and disasters. PEP stations are equipped with additional and backup communications equipment and power generators designed to enable them to continue broadcasting information to the public during and after an event.[54][55][56]

Beginning with WJR Detroit and WLW Cincinnati in 2016, FEMA began the process of constructing transportable studio shelters at the transmitters of 33 PEP stations, which feature broadcasting equipment, emergency provisions, a rest area, and an air filtration system. NPWS project manager Manny Centeno explained that these shelters were designed to "[expand] the survivability of these stations to include an all hazards platform, which means chemical, biological, radiological air protection and protection from electromagnetic pulse."[54][55][56]

Communication links

edit

The FEMA National Radio System (FNARS) "Provides Primary Entry Point service to the Emergency Alert System", and acts as an emergency presidential link into the EAS. The FNARS net control station is located at the Mount Weather Emergency Operations Center.[57]

Once an EAN is received by an EAS participant from a PEP station (or any other participant) the message then "daisy chains" through the network of participants. "Daisy chains" form when one station receives a message from multiple other stations and the station then forwards that message to multiple other stations. This process creates many redundant paths through which the message may flow, increasing the likelihood that the message will be received by all participants and adding to the survivability of the system. Each EAS participant is required to monitor at least two other participants.

EAS header

edit

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 that 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 EAS attention tone, which lasts between 8 and 25 seconds, depending on the originating station. The tone is 1,050 Hzⓘ on a NOAA Weather Radio station. On commercial broadcast stations, a "two-tone"ⓘ attention signal of 853 Hz and 960 Hz sine waves is used instead, the same signal used by the older Emergency Broadcast System. These tones have become infamous, and can be considered both frightening and annoying by listeners; in fact, the two tones, which form approximately the interval of a just major second at an unusually high pitch, were chosen specifically for their ability to draw attention, due to their unpleasantness on the human ear. The SAME header is equally known for its shrillness, which many have found to be startling. These tones are illegal to play on television or radio when there is not an actual emergency; doing so would result in disciplinary action or be fined for misuse or unauthorized playback of the tones (see "Tone usage outside of alerts" section below).[58] The "two-tone" system is no longer required as of 1998, and is to be used only for audio alerts before EAS messages.[59] Like the EBS, the attention signal is followed by a voice message describing the details of the alert.

The message ends with 3 bursts of the AFSK "EOM", or End of Message, which is the text NNNN, preceded each time by the binary 10101011 calibration.

IPAWS

edit

Under a 2006 executive order issued by George W. Bush, the U.S. government was instructed to create "an effective, reliable, integrated, flexible, and comprehensive" public warning system. This was accomplished via expansions to the aforementioned PEP network, and the development of the Integrated Public Alert and Warning System (IPAWS)—a national aggregator and distributor of alert information using the XML-based Common Alerting Protocol (CAP) and an internet network. IPAWS can be used to distribute alert information to EAS participants, supported mobile phones (Wireless Emergency Alerts), and other platforms.[60] IPAWS also allows the audio portion of an EAS message to utilize higher quality digital audio, rather than needing to carry the audio off-air from the originating station.[61][62]

Under an FCC report and order issued in 2007, EAS participants would be required to migrate to digital equipment supporting CAP within 180 days of the specification's adoption by FEMA. This was originally scheduled for September 30, 2010, but the deadline was later delayed to June 30, 2012 at the request of broadcasters.[63]

The FCC has established that IPAWS is not a full substitute for the SAME protocol, as it is vulnerable to situations that may make internet connectivity unavailable. Therefore, as a backup distribution path, broadcasters must also convert CAP messages to SAME headers to enable backwards compatibility with the existing "daisy chain" method of EAS distribution.[63][64]

In December 2021, the FCC issued a notice of proposed rulemaking seeking to prioritize the display of alert audio and text from CAP messages, in order to provide higher quality alert audio, improve parity between the visual display and audio for the benefit of the hearing impaired, and to reduce the amount of technical jargon contained within the visual display.[65][61] The rules were enacted in September 2022, with a deadline of December 12, 2023, for compliance;[62] the FCC later granted an extension to some broadcasters due to a delay in the release of associated software updates by EAS decoder vendor Sage.[65]