Specific Area Message Encoding

Specific Area Message Encoding (SAME) is a protocol used for framing and classification of broadcast emergency warning messages. It was developed by the United States National Weather Service for use on its NOAA Weather Radio (NWR) network, and was later adopted by the Federal Communications Commission for the Emergency Alert System, then subsequently by Environment Canada for use on its Weatheradio Canada service. It is also used to set off receivers in Mexico City and surrounding areas as part of the Mexican Seismic Alert System (SASMEX).

History

From the 1960s to the 1980s, a special feature of the NOAA Weather Radio (NWR) system was the transmission of a single 1050 Hz  attention tone prior to the broadcast of any message alerting the general public of significant weather events. This became known as the Warning Alarm Tone (WAT). Although it served NWR well, there were many drawbacks. Without staff at media facilities to manually evaluate the need to rebroadcast an NWR message using the Emergency Broadcast System (EBS), automatic rebroadcasting of all messages preceded by just the WAT was unacceptable and impractical. Even if stations and others with the need were willing to allow for this type of automatic capture, assuming the events for activation were critical, there was no way for automated equipment at the station to know when the message was complete and restore it back to normal operation.

SAME had its beginnings in the early 1980s when NOAA's National Weather Service (NWS) began experimenting with system using analog tones in a dual-tone multi-frequency (DTMF) format to transmit data with radio broadcasts.[1] In 1985, the NWS forecast offices began experimenting with placing special digital codes at the beginning and end of every message concerning life- or property-threatening weather conditions targeting a specific area. The intent of what became SAME was to ultimately transmit a code with the initial broadcast of all NWR messages. However, the roll-out moved slowly until 1995, when the U.S. Government provided the budget needed to develop the SAME technology across the entire radio network. Nationwide implementation occurred in 1997, when the Federal Communications Commission (FCC) adopted the SAME standard as part of its new Emergency Alert System (EAS).[2] In 2003, NOAA established a SAME technology standard for weather radio receivers.

The SAME technique was later adopted by the U.S. Federal Communications Commission (FCC) in 1997[3] for use in the EAS as well as by Environment Canada [4] for its Weatheradio Canada service in 2004. Much like the original EBS dual-tone Attention Signal , this produces a distinct sound (the SAME header ) which is easily recognized by most individuals due to its use in weekly and monthly broadcast tests, as well as weather alert messages. During the said events, viewers and/or listeners will hear these digital codes in the form of buzzes, chirps, and clicking sounds (or what broadcast engineers affectionately call "duck farts")[5] just before the attention signal is sent out and at the conclusion of the voice message.[6]

Format of digital parts

In the SAME system, messages are constructed in four parts, the first and last of which are digital and the middle two are audio. The digital sections of a SAME message are AFSK data bursts, with individual bits lasting 1920 μs (1.92 ms) each, giving a bit rate of 52056 bits per second. A mark bit is four complete cycles of a sine wave, translating to a mark frequency of 208313 Hz, and a space bit is three complete sine wave cycles, making the space frequency 1562.5 Hz.

The data is sent isochronously and encoded in 8-bit bytes with the most-significant bit of each ASCII byte set to zero. The least-significant bit of each byte is transmitted first, including the preamble. The data stream is bit and byte synchronized on the preamble.[7]

Since there is no error correction, the digital part of a SAME message is transmitted 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.

Header format

The text of the header code is a fixed format:

<Preamble>ZCZC-ORG-EEE-PSSCCC+TTTT-JJJHHMM-LLLLLLLL-

This is broken down as follows:

1. A preamble of binary 10101011 (0xAB in hex) repeated sixteen times, used for "receiver calibration" (i.e., clock synchronization), then the letters ZCZC as an attention to the decoder (a message activation method inherited from NAVTEX).

2. ORG — Originator code; programmed per unit when put into operation[8]

  • PEP – Primary Entry Point Station
    • President or other authorized national officials
  • CIV – Civil authorities
    • i.e. Governor, state/local emergency management, local police/fire officials
  • WXR – National Weather Service (or Environment Canada.)
    • Any weather-related alert
  • EAS – EAS Participant
    • Broadcasters. Generally only used with test messages.
  • EAN – Emergency Action Notification Network

3. EEE — Event code; programmed at time of event

4. PSSCCC — Location codes (up to 31 location codes per message), each beginning with a dash character; programmed at time of event

  • In the United States, the first digit (P) is zero if the entire county or area is included in the warning, otherwise, it is a non-zero number depending on the location of the emergency.[9] The remaining five digits are the FIPS state (SS) and county code (CCC). The entire state may be specified by using county code 000 (three zeros).
  • In Canada, all six digits make up a Canadian Location Code, which corresponds to a specific forecast region as used by the Meteorological Service of Canada. All forecast region numbers are six digits with the first digit always zero.

5. TTTT — Purge time of the alert event (from exact time of issue)

  • In the format hhmm, using 15 minute increments up to one hour, using 30 minute increments up to six hours, and using hourly increments beyond six hours. Weekly and monthly tests sometimes have a 12-hour or greater purge time to assure users have an ample opportunity to verify reception of the test event messages; however; 15 minutes is more common, especially on NOAA Weather Radio's tests.
  • For short term events (like a tornado) this value could be set to 0000 (four zeros), which will purge the warning immediately after the message has been received. However, this is not typical, and FCC guidelines suggest a minimum of 15 minutes purge time.
  • The purge time is not intended to coincide with the actual end of the event. Longer events that may not end for days (like hurricanes) may have a purge time of only a few hours. That an event message has been purged does not indicate or imply that the threat has passed.

6. JJJHHMM — Exact time of issue, in UTC, (without time zone adjustments).

  • JJJ is the Ordinal date (day) of the year, with leading zeros
  • HHMM is the hours and minutes (24-hour format), in UTC, with leading zeros

7. LLLLLLLL — Eight-character station callsign identification, with "/" used instead of "–" (such as the first eight letters of a cable headend's location, WABC/FM for WABC-FM, KLOX/NWS for a weather radio station programmed from Los Angeles, or EC/GC/CA for a Weatheradio Canada station).

Each field of the header code is terminated by a dash character, including the station ID at the end; individual PSSCCC location numbers are also separated by dashes, with a plus (+) separating the last location from the purge time that follows it.

Full message format

An EAS message contains these elements, in this transmitted sequence:

  1. Header.
  2. Attention signal — Sent if any message is included (normally sent with all messages except RWT on broadcast radio/TV); must be at least eight seconds long. (On Weatheradio in Canada the 1050 Hz tone is only used with three event codes: RMT, SVR & TOR.)
  3. Message — Audio, video image or video text.
  4. Tail — (Preamble) NNNN (EOM).

There is one second of blank audio between each section, and before and after each message. For those used to packet communications systems where each packet has a checksum, note that there is no checksum used in the message format. Each message is supposed to be transmitted 3 times, and the receiver is obliged to implement columnar parity correction.

The combined tones date back to 1976 when they were made part of the Emergency Broadcast System, the EAS' predecessor.

Event codes

There are roughly 80 different event codes that are used in EAS. These codes are defined federally by the FCC for use in the EAS system and publicly by the Consumer Electronics Association (CEA) standard[10] for SAME protocol weather radio receiver decoder units.

All but the first six of these used to be optional and could be programmed into encoder/decoder units at the request of the broadcaster. However, a July 12, 2007 memo by the FCC now requires mandatory participation in state and local level EAS by broadcasters. Furthermore, the creation and evolution of a voluntary standard by the CEA in December 2003 has provided participating manufacturers of weather radio receivers a single definitive reference to use when designing and programming receivers. In addition, some receiver manufacturers have added an additional layer as to whether or not an event code can be user-suppressed (e.g., a Hurricane Warning in a Midwest US State) or will never be allowed to be suppressed (e.g., nuclear power plant warning).

Key for event code tables
USA type key CAN/MEX type key Event level key
MMandatory code ABAdministrative bulletin ADVAdvisory
O1Original optional code CICurrently implemented WCHWatch
O22002 optional code[11][12] RTRequired test WRNWarning
O32017 optional code[13] FIFor future implementation TESTTest
NINot implemented NINot implemented
TSTesting for Implementation
Event codes in use:
The following event codes have been implemented by agencies in the United States and/or Canada, and CIRES A.C. in Mexico.
Event Code U.S. Type CAN. Type MEX. Type Event Description Event Level
ADRO1ABNIAdministrative messageADV
AVAO2FINIAvalanche watchWCH
AVWO2FINIAvalanche warningWRN
BLUO3NINIBlue alert (see note below **** )WRN
BZWO1CINIBlizzard warningWRN
CAEO2FINIChild abduction emergencyADV
CDWO2FINICivil danger warningWRN
CEMO1FINICivil emergency messageWRN
CFAO2FINICoastal flood WatchWCH
CFWO2FINICoastal flood warningWRN
DMOO1ABNIDemonstration messageTEST
DSWO2CINIDust storm warningWRN
EANMFINIEmergency action notification (Begins a nationwide EAS activation) (not implemented on most NWR stations.[14])WRN
EATNIFINIEmergency action termination (previously ended a nationwide EAS activation *****)WRN
EQWO2FICIEarthquake warning (See note below *** )WRN
EVIO1FINIEvacuation immediateWRN
EWWO3NINIExtreme wind warningWRN
FFAO1FINIFlash flood watchWCH
FFSO1FINIFlash flood StatementADV
FFWO1FINIFlash flood warningWRN
FLAO1FINIFlood watchWCH
FLSO1FINIFlood statementADV
FLWO1FINIFlood warningWRN
FRWO2FINIFire warningWRN
FSWNICINIFlash freeze warningWRN
FZWNICINIFreeze warning (in Canada, 'Frost warning' – see note below ** )WRN
HLSO1FITSHurricane local statementADV
HMWO2FINIHazardous materials warningWRN
HUAO1CITSHurricane watchWCH
HUWO1CITSHurricane warningWRN
HWAO1FINIHigh wind watchWCH
HWWO1CINIHigh wind warningWRN
LAEO2FINILocal area emergencyADV
LEWO2FINILaw enforcement warningWRN
NATNIABNINational audible testTEST
NICMABNINational Information Center statement (used to follow up an EAN)ADV
NMNO2ABNINetwork message notificationADV
NPTMABNINational periodic testTEST
NSTNIABNINational silent testTEST
NUWO2FININuclear power plant warningWRN
RHWO2FINIRadiological hazard warningWRN
RMTMRTNIRequired monthly testTEST
RWTMRTCIRequired weekly testTEST
SMWO2TSNISpecial marine warningWRN
SPSO1FINISpecial weather statementADV
SPWO2FINIShelter in place warningWRN
SQWO1CINISnowsquall warningWRN
SSAO3NINIStorm surge watchWCH
SSWO3NINIStorm surge warningWRN
SVAO1CINISevere thunderstorm watchWCH
SVRO1CINISevere thunderstorm warningWRN
SVSO1TSNISevere weather statement (U.S., CAN)ADV
TOAO1CINITornado watchWCH
TOEO2FINI9-1-1 telephone outage emergencyADV
TORO1CINITornado warning[15]WRN
TRAO2CINITropical storm watchWCH
TRWO2CINITropical storm warningWRN
TSAO1TSNITsunami watchWCH
TSWO1TSNITsunami warningWRN
VOWO2FICIVolcano warning (see note below *** )WRN
WSAO1CINIWinter storm watchWCH
WSWO1CINIWinter storm warning (Canada, see note below † )WRN
??AO2CINIUnrecognized watchWCH
??EO2CINIUnrecognized emergencyADV
??SO2CINIUnrecognized statementADV
??WO2CINIUnrecognized warningWRN
??MO2CINIUnrecognized messageADV
** While the CEA standard[10] lists the FZW event code as "Freeze Warning", Environment Canada refers to it[16] as a "Frost Warning". However, it will be displayed as a "Freeze Warning" on receivers that are compliant to the CEA standard.
Environment Canada additionally uses[16] the WSW event code to refer to any of the following weather conditions: Blowing Snow Warning, Freezing Drizzle Warning, Freezing Rain Warning, Snowfall Warning, Snow Squall Warning
*** The EQW and VOW event codes are used in Mexico as part of the Mexican Seismic Alert System (also known as SASMEX). EQW is referred as "Alerta Sísmica", while VOW is referred to as "Alerta Volcánica".[17] Other event codes are being tested, such as Hurricane Warning (HUW), Hurricane Watch (HUA) and Hurricane Statement (HLS). Required Weekly Tests (RWT) are conducted every three hours to make sure receivers are working properly.[18]
**** The FCC created the BLU code for Blue Alerts beginning on December 14, 2017. [19]
*****The FCC in 2012 modified protocol for national EAS activations. Emergency Action Notifications are now treated as any other EAS alert (except that it is mandatory to air), eliminating the need for Emergency Action Terminations, so the FCC removed it from operation.
Internal use only:
Receiver decoders that comply to the CEA standard[10] will neither display the messages below, nor activate a warning tone if applicable. While the message will be stored in memory, it will not be displayed to the user. The FCC has also designated[11] these event codes as being for "internal use only", and not for display. Environment Canada lists[16] these messages as "Administrative Bulletins".
Event Code U.S. Type CAN. Type Event Description Event Level
TXBO2ABTransmitter backup onADV
TXFO2ABTransmitter carrier offADV
TXOO2ABTransmitter carrier onADV
TXPO2ABTransmitter primary onADV
Future implementation:
The following codes are part of the CEA standard[10] for receiver decoders, but are not listed as being in use by any agencies in the United States. Environment Canada lists[16] these codes as being "for future implementation". None of these event codes are being implemented in Mexico, as Mexico's network is for seismic and volcanic alerts at this time.
Event Code U.S. Type CAN. Type Event Description Event Level
BHWNIFIBiological hazard warningWRN
BWWNIFIBoil water warningWRN
CHWNIFIChemical hazard warningWRN
CWWNIFIContaminated water warningWRN
DBANIFIDam watchWCH
DBWNIFIDam break warningWRN
DEWNIFIContagious disease warningWRN
EVANIFIEvacuation watchWCH
FCWNIFIFood contamination warningWRN
IBWNIFIIceberg warningWRN
IFWNIFIIndustrial fire warningWRN
LSWNIFILandslide warningWRN
POSNIFIPower outage statementADV
WFANIFIWild fire watchWCH
WFWNIFIWild fire warningWRN

The FCC established naming conventions for EAS event codes. The third letter of the code must be one of the following.[20]

Third letter of event code Category Description
WWarningAn event that alone poses a significant threat to public safety and/or property, probability of occurrence and location is high, and the onset time is relatively short.
AWatchMeets the classification of a warning, but either the onset time, probability of occurrence, or location is uncertain.
EEmergencyAn event that, by itself, would not kill or injure or do property damage, but indirectly may cause other things to happen that result in a hazard.
SStatementA message containing follow up information to a warning, watch, or emergency.

The exception to this convention is for "TOR" (tornado warning), "SVR" (severe thunderstorm warning), "EVI" (evacuation immediate), the EAS national activation codes, and administrative messages.[11]

On weather radio receivers

An example of a SAME alert weather radio receiver.

There are many weather/all-hazards radio receivers that are equipped with the SAME alert feature, which allows users to program SAME/FIPS/CLC codes for their designated area or areas of their interest and/or concern rather than the entire broadcast area. (For example, a person living in Irving, Texas, would program a FIPS code for Dallas County. However, if there is a need to know of severe weather from the west and northwest ahead of time, the user would program additional FIPS codes for Denton and Tarrant Counties.)

On a more specialized receiver, a user has the option to eliminate any SAME alert codes that may not apply to their area such as a "Special Marine Warning" or a "Coastal Flood Warning". Once the SAME header is sent by NOAA/NWS and if it matches the desired code(s), the receivers then decode the event, scroll it on their display screens, and sound an alarm.

Receivers receive on one of the following National Weather Service network frequencies (in MHz): 162.400, 162.425, 162.450, 162.475, 162.500, 162.525, and 162.550. The signals are typically receivable up to 40 miles (80 km) from the transmitters.[21]

See also

  • Common Alerting Protocol (CAP) – A SAME-compatible digital format for multi-system warning coordination.
  • METAR – The international meteorological code for an aviation routine weather report.

References

  1. Nelson, W.C. (2002). "American Warning Dissemination and NOAA Weather Radio".
  2. "The History of NOAA Weather Radio". Weather Radios Direct. Retrieved 13 May 2014.
  3. NOAA Weather Radio - Watches, Warnings and Tones/Alarms National Weather Service in Philadelphia/Mount Holly (accessed October 1, 2009)
  4.  – The Green Lane: (Backgrounder) – Weatheradio Network (accessed Dec. 5, 2011)
  5. http://www.wsab.org/eas/eas_meeting_minutes_jan06.html
  6. WRSAME – Weather Radio Specific Area Message Encoder Archived 2013-04-15 at Archive.today Metro Skywarn (accessed August 20, 2009)
  7. http://www.nws.noaa.gov/directives/sym/pd01017012curr.pdf
  8. 47CFR11.31(d)
  9. http://www.gpo.gov/fdsys/pkg/CFR-2010-title47-vol1/xml/CFR-2010-title47-vol1-sec11-31.xml
  10. Consumer Electronics Association (CEA) Technology Standard "CEA-2009-B (ANSI)", November 2010, accessed January 11, 2014.
  11. "Federal Communications Commission Report and Order" (PDF). February 22, 2002. Retrieved September 22, 2012.
  12. http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=75127c72007aa6a3f1ce8fda8cb814e2&rgn=div5&view=text&node=47:1.0.1.1.11&idno=47#47:1.0.1.1.11.2.239.1
  13. "Federal Communications Commission Report and Order" (PDF). July 11, 2016. Retrieved August 30, 2017.
  14. Emergency Action Notifications are implemented on some Pacific Northwest NWR Stations. These stations are connected to EAS Encoder/Decoder systems (ENDECs) that relay national and regional alerts without NWS having to issue them. NWS Seattle has an ENDEC in their forecast office while other stations have ENDECs connected from the EM of the county station is located in. It is being worked on with WFO Spokane to get an ENDEC implemented in their office for their seven NWR stations.
  15. The National Weather Service additionally uses the TOR event code to refer to an Extreme Wind Warning. See http://www.nws.noaa.gov/os/vtec/pdfs/EWWInstructions.pdf
  16. Environment Canada – Weather and Meteorology "SAME Event Codes"
  17. https://www.youtube.com/watch?v=Ogv9gs6-asA
  18. https://www.youtube.com/watch?v=oG8ZEbU3WYE
  19. "Blue Alert EAS Event Code". January 18, 2018. Retrieved February 1, 2019.
  20. National Weather Service , accessed September 22, 2012.
  21. NWR Specific Area Message Encoding (SAME), https://www.weather.gov/nwr/nwrsame
  22. "Cyclone Weather Alert for Texas Longhorns Fans". Youtube. Retrieved 2020-01-08.
  23. "Knowing: Trailer #2". IMDb. Retrieved 2020-01-08.
  24. "MMK License LLC Agrees to Settle EAS Investigation". Federal Communications Commission. 2015-12-11. Retrieved 2020-01-08.
  25. Eggerton, John (November 5, 2013). "FCC Proposes Fining TBS $25,000 Over 'Conan' Promo". Broadcasting & Cable. Retrieved 2020-01-08.
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