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Electronic Code of Federal Regulations

e-CFR data is current as of September 19, 2019

Title 47Chapter ISubchapter APart 11Subpart B → §11.31


Title 47: Telecommunication
PART 11—EMERGENCY ALERT SYSTEM (EAS)
Subpart B—Equipment Requirements


§11.31   EAS protocol.

(a) The EAS uses a four part message for an emergency activation of the EAS. The four parts are: Preamble and EAS Header Codes; audio Attention Signal; message; and, Preamble and EAS End Of Message (EOM) Codes.

(1) The Preamble and EAS Codes must use Audio Frequency Shift Keying at a rate of 520.83 bits per second to transmit the codes. Mark frequency is 2083.3 Hz and space frequency is 1562.5 Hz. Mark and space time must be 1.92 milliseconds. Characters are ASCII seven bit characters as defined in ANSI X3.4-1977 ending with an eighth null bit (either 0 or 1) to constitute a full eight-bit byte.

(2) The Attention Signal must be made up of the fundamental frequencies of 853 and 960 Hz. The two tones must be transmitted simultaneously. The Attention Signal must be transmitted after the EAS header codes.

(3) The message may be audio, video or text.

(b) The ASCII dash and plus symbols are required and may not be used for any other purpose. Unused characters must be ASCII space characters. FM or TV call signs must use a slash ASCII character number 47 (/) in lieu of a dash.

(c) The EAS protocol, including any codes, must not be amended, extended or abridged without FCC authorization. The EAS protocol and message format are specified in the following representation.

Examples are provided in FCC Public Notices.

[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTT-JJJHHMM-LLLLLLLL-(one second pause)

[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTTpJJJHHMM-LLLLLLLL-(one second pause)

[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTT-JJJHHMM-LLLLLLLL-(at least a one second pause)

(transmission of 8 to 25 seconds of Attention Signal)

(transmission of audio, video or text messages)

(at least a one second pause)

[PREAMBLE]NNNN (one second pause)

[PREAMBLE]NNNN (one second pause)

[PREAMBLE]NNNN (at least one second pause)

[PREAMBLE] This is a consecutive string of bits (sixteen bytes of AB hexadecimal [8 bit byte 10101011]) sent to clear the system, set AGC and set asynchronous decoder clocking cycles. The preamble must be transmitted before each header and End of Message code.

ZCZC—This is the identifier, sent as ASCII characters ZCZC to indicate the start of ASCII code.

ORG—This is the Originator code and indicates who originally initiated the activation of the EAS. These codes are specified in paragraph (d) of this section.

EEE—This is the Event code and indicates the nature of the EAS activation. The codes are specified in paragraph (e) of this section. The Event codes must be compatible with the codes used by the NWS Weather Radio Specific Area Message Encoder (WRSAME).

PSSCCC—This is the Location code and indicates the geographic area affected by the EAS alert. There may be 31 Location codes in an EAS alert. The Location code uses the codes described in the American National Standards Institute (ANSI) standard, ANSI INCITS 31-2009 (“Information technology—Codes for the Identification of Counties and Equivalent Areas of the United States, Puerto Rico, and the Insular Areas”). Each state is assigned an SS number as specified in paragraph (f) of this section. Each county and some cities are assigned a CCC number. A CCC number of 000 refers to an entire State or Territory. P defines county subdivisions as follows: 0 = all or an unspecified portion of a county, 1 = Northwest, 2 = North, 3 = Northeast, 4 = West, 5 = Central, 6 = East, 7 = Southwest, 8 = South, 9 = Southeast. Other numbers may be designated later for special applications. The use of county subdivisions will probably be rare and generally for oddly shaped or unusually large counties. Any subdivisions must be defined and agreed to by the local officials prior to use.

+ TTTT—This indicates the valid time period of a message in 15 minute segments up to one hour and then in 30 minute segments beyond one hour; i.e., + 0015, + 0030, + 0045, + 0100, + 0430 and + 0600.

JJJHHMM—This is the day in Julian Calendar days (JJJ) of the year and the time in hours and minutes (HHMM) when the message was initially released by the originator using 24 hour Universal Coordinated Time (UTC).

LLLLLLLL—This is the identification of the EAS Participant, NWS office, etc., transmitting or retransmitting the message. These codes will be automatically affixed to all outgoing messages by the EAS encoder.

NNNN—This is the End of Message (EOM) code sent as a string of four ASCII N characters.

(d) The only originator codes are:

Originator ORG code
EAS ParticipantEAS
Civil authoritiesCIV
National Weather ServiceWXR
Primary Entry Point SystemPEP

(e) The following Event (EEE) codes are presently authorized:

Nature of activationEvent codes
National Codes (Required):
Emergency Action Notification (National only)EAN.
National Information CenterNIC
National Periodic TestNPT.
Required Monthly TestRMT.
Required Weekly TestRWT.
State and Local Codes (Optional):
Administrative MessageADR.
Avalanche WarningAVW.
Avalanche WatchAVA.
Blizzard WarningBZW.
Blue AlertBLU.
Child Abduction EmergencyCAE.
Civil Danger WarningCDW.
Civil Emergency MessageCEM.
Coastal Flood WarningCFW.
Coastal Flood WatchCFA.
Dust Storm WarningDSW.
Earthquake WarningEQW.
Evacuation ImmediateEVI.
Extreme Wind WarningEWW.
Fire WarningFRW.
Flash Flood WarningFFW.
Flash Flood WatchFFA.
Flash Flood StatementFFS.
Flood WarningFLW.
Flood WatchFLA.
Flood StatementFLS.
Hazardous Materials WarningHMW.
High Wind WarningHWW.
High Wind WatchHWA.
Hurricane WarningHUW.
Hurricane WatchHUA.
Hurricane StatementHLS.
Law Enforcement WarningLEW.
Local Area EmergencyLAE.
Network Message NotificationNMN.
911 Telephone Outage EmergencyTOE.
Nuclear Power Plant WarningNUW.
Practice/Demo WarningDMO.
Radiological Hazard WarningRHW.
Severe Thunderstorm WarningSVR.
Severe Thunderstorm WatchSVA.
Severe Weather StatementSVS.
Shelter in Place WarningSPW
Special Marine WarningSMW.
Special Weather StatementSPS.
Storm Surge WatchSSA.
Storm Surge WarningSSW.
Tornado WarningTOR.
Tornado WatchTOA.
Tropical Storm WarningTRW.
Tropical Storm WatchTRA.
Tsunami WarningTSW.
Tsunami WatchTSA.
Volcano WarningVOW.
Winter Storm WarningWSW.
Winter Storm WatchWSA.

(f) The All U.S., State, Territory and Offshore (Marine Area) ANSI number codes (SS) are as follows. County ANSI numbers (CCC) are contained in the State EAS Mapbook.

   ANSI No.
All U.S00
State:
AL01
AK02
AZ04
AR05
CA06
CO08
CT09
DE10
DC11
FL12
GA13
HI15
ID16
IL17
IN18
IA19
KS20
KY21
LA22
ME23
MD24
MA25
MI26
MN27
MS28
MO29
MT30
NE31
NV32
NH33
NJ34
NM35
NY36
NC37
ND38
OH39
OK40
OR41
PA42
RI44
SC45
SD46
TN47
TX48
UT49
VT50
VA51
WA53
WV54
WI55
WY56
Terr.:
AS60
FM64
GU66
MH68
PR72
PW70
UM74
VI78
Offshore (Marine Areas)1
Eastern North Pacific Ocean, and along U.S. West Coast from Canadian border to Mexican border57
North Pacific Ocean near Alaska, and along Alaska coastline, including the Bering Sea and the Gulf of Alaska58
Central Pacific Ocean, including Hawaiian waters59
South Central Pacific Ocean, including American Samoa waters61
Western Pacific Ocean, including Mariana Island waters65
Western North Atlantic Ocean, and along U.S. East Coast, from Canadian border south to Currituck Beach Light, N.C73
Western North Atlantic Ocean, and along U.S. East Coast, south of Currituck Beach Light, NC, following the coastline to Ocean Reef, FL, including the Caribbean75
Gulf of Mexico, and along the U.S. Gulf Coast from the Mexican border to Ocean Reef, FL77
Lake Superior91
Lake Michigan92
Lake Huron93
Lake St. Clair94
Lake Erie96
Lake Ontario97
St. Lawrence River above St. Regis98

1The numbers assigned to the offshore marine areas listed in this table are not described under the ANSI standard, but rather are numeric codes that were assigned by the National Weather Service.

[59 FR 67092, Dec. 28, 1994, as amended at 60 FR 55999, Nov. 6, 1995; 61 FR 54952, Oct. 23, 1996; 63 FR 29663, June 1, 1998; 67 FR 18508, Apr. 16, 2002; 67 FR 77174, Dec. 17, 2002; 69 FR 72031, Dec. 10, 2004; 70 FR 71033, Nov. 25, 2005; 77 FR 16701, Mar. 22, 2012; 80 FR 37174, June 30, 2015; 81 FR 53043, Aug. 11, 2016; 83 FR 2563, Jan. 18, 2018]

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