{"data":{"id":"us/47-cfr-11.31","jurisdiction":"us","citation":"47 CFR 11.31","heading":"EAS protocol.","body":"(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.\n(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.\n(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.\n(3) The message may be audio, video or text.\n(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.\n(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.\nExamples are provided in FCC Public Notices.\n[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTT-JJJHHMM-LLLLLLLL-(one second pause)\n[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTTpJJJHHMM-LLLLLLLL-(one second pause)\n[PREAMBLE]ZCZC-ORG-EEE-PSSCCC + TTTT-JJJHHMM-LLLLLLLL-(at least a one second pause)\n(transmission of 8 to 25 seconds of Attention Signal)\n(transmission of audio, video or text messages)\n(at least a one second pause)\n[PREAMBLE]NNNN (one second pause)\n[PREAMBLE]NNNN (one second pause)\n[PREAMBLE]NNNN (at least one second pause)\n[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.\nZCZC—This is the identifier, sent as ASCII characters ZCZC to indicate the start of ASCII code.\nORG—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.\nEEE—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).\nPSSCCC—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.\n+ 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.\nJJJHHMM—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).\nLLLLLLLL—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.\nNNNN—This is the End of Message (EOM) code sent as a string of four ASCII N characters.\n(d)(1) The only originator codes are:\nTable 1 to Paragraph (d)(1)\nOriginator ORG code\nEAS Participant EAS\nCivil authorities CIV\nNational Weather Service WXR\nUnited States Government PEP\n(2) [Reserved]\n(e) The following Event (EEE) codes are presently authorized:\nTable 2 to Paragraph (e)\nNature of activation Event codes\nNational Codes (Required):\nEmergency Action Notification (National only) EAN.\nNational Information Center NIC.\nNational Periodic Test NPT.\nRequired Monthly Test RMT.\nRequired Weekly Test RWT.\nState and Local Codes (Optional):\nAdministrative Message ADR.\nAvalanche Warning AVW.\nAvalanche Watch AVA.\nBlizzard Warning BZW.\nBlue Alert BLU.\nChild Abduction Emergency CAE.\nCivil Danger Warning CDW.\nCivil Emergency Message CEM.\nCoastal Flood Warning CFW.\nCoastal Flood Watch CFA.\nDust Storm Warning DSW.\nEarthquake Warning EQW.\nEvacuation Immediate EVI.\nExtreme Wind Warning EWW.\nFire Warning FRW.\nFlash Flood Warning FFW.\nFlash Flood Watch FFA.\nFlash Flood Statement FFS.\nFlood Warning FLW.\nFlood Watch FLA.\nFlood Statement FLS.\nHazardous Materials Warning HMW.\nHigh Wind Warning HWW.\nHigh Wind Watch HWA.\nHurricane Warning HUW.\nHurricane Watch HUA.\nHurricane Statement HLS.\nLaw Enforcement Warning LEW.\nLocal Area Emergency LAE.\nMissing and Endangered Persons MEP.\nNetwork Message Notification NMN.\n911 Telephone Outage Emergency TOE.\nNuclear Power Plant Warning NUW.\nPractice/Demo Warning DMO.\nRadiological Hazard Warning RHW.\nSevere Thunderstorm Warning SVR.\nSevere Thunderstorm Watch SVA.\nSevere Weather Statement SVS.\nShelter in Place Warning SPW.\nSpecial Marine Warning SMW.\nSpecial Weather Statement SPS.\nStorm Surge Watch SSA.\nStorm Surge Warning SSW.\nTornado Warning TOR.\nTornado Watch TOA.\nTropical Storm Warning TRW.\nTropical Storm Watch TRA.\nTsunami Warning TSW.\nTsunami Watch TSA.\nVolcano Warning VOW.\nWinter Storm Warning WSW.\nWinter Storm Watch WSA.\n(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.\nTable 3 to Paragraph (f)\nANSI No.\nAll U.S 00\nState:\nAL 01\nAK 02\nAZ 04\nAR 05\nCA 06\nCO 08\nCT 09\nDE 10\nDC 11\nFL 12\nGA 13\nHI 15\nID 16\nIL 17\nIN 18\nIA 19\nKS 20\nKY 21\nLA 22\nME 23\nMD 24\nMA 25\nMI 26\nMN 27\nMS 28\nMO 29\nMT 30\nNE 31\nNV 32\nNH 33\nNJ 34\nNM 35\nNY 36\nNC 37\nND 38\nOH 39\nOK 40\nOR 41\nPA 42\nRI 44\nSC 45\nSD 46\nTN 47\nTX 48\nUT 49\nVT 50\nVA 51\nWA 53\nWV 54\nWI 55\nWY 56\nTerr.:\nAS 60\nFM 64\nGU 66\nMH 68\nPR 72\nPW 70\nUM 74\nVI 78\nOffshore (Marine Areas) 1\nEastern North Pacific Ocean, and along U.S. West Coast from Canadian border to Mexican border 57\nNorth Pacific Ocean near Alaska, and along Alaska coastline, including the Bering Sea and the Gulf of Alaska 58\nCentral Pacific Ocean, including Hawaiian waters 59\nSouth Central Pacific Ocean, including American Samoa waters 61\nWestern Pacific Ocean, including Mariana Island waters 65\nWestern North Atlantic Ocean, and along U.S. East Coast, from Canadian border south to Currituck Beach Light, N.C 73\nWestern North Atlantic Ocean, and along U.S. East Coast, south of Currituck Beach Light, NC, following the coastline to Ocean Reef, FL, including the Caribbean 75\nGulf of Mexico, and along the U.S. Gulf Coast from the Mexican border to Ocean Reef, FL 77\nLake Superior 91\nLake Michigan 92\nLake Huron 93\nLake St. Clair 94\nLake Erie 96\nLake Ontario 97\nSt. Lawrence River above St. Regis 98\n1 The 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.","path":["Title 47—Telecommunication","CHAPTER I—FEDERAL COMMUNICATIONS COMMISSION","SUBCHAPTER A—GENERAL","PART 11—EMERGENCY ALERT SYSTEM (EAS)","Subpart B—Equipment Requirements"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-47.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:28Z","sha256":"ee6bd69ffd92fac6bc9cbb5457dc7408cce11bad2a8f1ba7ff60859c48ecb154","source_id":"us-cfr","stale":true,"prev":"us/47-cfr-11.21","next":"us/47-cfr-11.32"},"notice":"GroundRules: Original legal text. Not legal advice."}