Specific Area Message Encoding

Specific Area Message Encoding (SAME) is the protocol used to encode the Emergency Alert System (EAS) and NOAA Weather Radio (NWR) in the U.S. and Weatheradio Canada in Canada. It is also used to set off receivers in Mexico City and surrounding areas as part of Mexico's Seismic Alert System (SASMEX) and Seismic Alert Radio System (SARMEX).

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. The NWS started implementing SAME on the full NWR system in 1998. In 2003, NOAA established a SAME technology standard for weather radio receivers. 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]

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, & 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 the digital parts
A sample SAME transmission
An example of SAME tones, with the header decoded as follows:

"A Required Weekly Test has been issued for the following counties/areas: Hillsborough FL, Manatee FL, Pasco FL, Pinellas FL, and Sarasota FL at 12:15 am EDT on October 5 effective until 12:45 am EDT. Message from WTSP/TV."
Problems playing this file? See media help.

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 burst, with each individual bit lasting 1920 μs (1.92 ms) each, giving a bit rate of 5205⁄6 bits per second. A mark bit is four complete cycles of a sine wave, translating to a mark frequency of 20831⁄3 Hz, and a space bit is three complete sine wave cycles, making the space frequency 1562.5 Hz.

The data is encoded in 7-bit ASCII but uses all 8-bits, with no parity bit and no stop bit ("8-N-0"). The least-significant bit of each byte is transmitted first, including the preamble.

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. However, consumer weather radio receivers often activate (unmute the audio) after hearing only one out of the three headers (with a significant delay).[upper-alpha 1]

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[7]

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

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

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

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, or KLOX/NWS for a weather radio station programmed from Los Angeles).

Each field of the header code is terminated by a dash character, including the station ID at the end; individual PSCCC 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.)
    • Single  1050 Hz  audio tone for Weatheradio.
    • Combined  853 and 960 Hz  tones for broadcast radio/TV.
  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[9] 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
M Mandatory code AB Administrative bulletin ADV Advisory
O1 Original optional code CI Currently implemented WCH Watch
O2 2002 optional code[10][11] RT Required test WRN Warning
NI Not implemented FI For future implementation TEST Test
TS Testing 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
ADR O1 AB NI Administrative Message ADV
AVA O2 FI NI Avalanche Watch WCH
AVW O2 FI NI Avalanche Warning WRN
BZW O1 CI NI Blizzard Warning WRN
CAE O2 FI NI Child Abduction Emergency ADV
CDW O2 FI NI Civil Danger Warning WRN
CEM O1 FI NI Civil Emergency Message WRN
CFA O2 FI NI Coastal Flood Watch WCH
CFW O2 FI NI Coastal Flood Warning WRN
DMO O1 AB NI Demonstration Message TEST
DSW O2 CI NI Dust Storm Warning WRN
EAN M FI NI Emergency Action Notification (Begins a nationwide EAS activation) (not implemented on most NWR stations.[12]) WRN
EAT M FI NI Emergency Action Termination (Ends a nationwide EAS activation) (not implemented on most NWR stations.[12]) WRN
EQW O2 FI CI Earthquake Warning (See note below *** ) WRN
EVI O1 FI NI Evacuation Immediate WRN
FFA O1 FI NI Flash Flood Watch WCH
FFS O1 FI NI Flash Flood Statement ADV
FFW O1 FI NI Flash Flood Warning WRN
FLA O1 FI NI Flood Watch WCH
FLS O1 FI NI Flood Statement ADV
FLW O1 FI NI Flood Warning WRN
FRW O2 FI NI Fire Warning WRN
FSW NI CI NI Flash Freeze Warning WRN
FZW NI CI NI Freeze Warning (in Canada, 'Frost Warning' - See note below ** ) WRN
HLS O1 FI TS Hurricane Local Statement ADV
HMW O2 FI NI Hazardous Materials Warning WRN
HUA O1 CI TS Hurricane Watch WCH
HUW O1 CI TS Hurricane Warning WRN
HWA O1 FI NI High Wind Watch WCH
HWW O1 CI NI High Wind Warning WRN
LAE O2 FI NI Local Area Emergency ADV
LEW O2 FI NI Law Enforcement Warning WRN
NAT NI AB NI National Audible Test TEST
NIC M AB NI National Information Center Statement (Used to follow up an EAN) ADV
NMN O2 AB NI Network Message Notification ADV
NPT M AB NI National Periodic Test TEST
NST NI AB NI National Silent Test TEST
NUW O2 FI NI Nuclear Power Plant Warning WRN
RHW O2 FI NI Radiological Hazard Warning WRN
RMT M RT NI Required Monthly Test TEST
RWT M RT CI Required Weekly Test TEST
SMW O2 TS NI Special marine warning WRN
SPS O1 FI NI Special Weather Statement ADV
SPW O2 FI NI Shelter In-place Warning WRN
SVA O1 CI NI Severe Thunderstorm Watch WCH
SVR O1 CI NI Severe Thunderstorm Warning WRN
SVS O1 TS NI Severe Weather Statement (U.S., CAN) ADV
TOA O1 CI NI Tornado Watch WCH
TOE O2 FI NI 911 Telephone Outage Emergency ADV
TOR O1 CI NI Tornado Warning[13] WRN
TRA O2 CI NI Tropical Storm Watch WCH
TRW O2 CI NI Tropical Storm Warning WRN
TSA O1 TS NI Tsunami Watch WCH
TSW O1 TS NI Tsunami Warning WRN
VOW O2 FI CI Volcano Warning (See note below *** ) WRN
WSA O1 CI NI Winter Storm Watch WCH
WSW O1 CI NI Winter Storm Warning (Canada, see note below † ) WRN
??A O2 CI NI Unrecognized Watch WCH
??E O2 CI NI Unrecognized Emergency ADV
??S O2 CI NI Unrecognized Statement ADV
??W O2 CI NI Unrecognized Warning WRN
??M O2 CI NI Unrecognized Message ADV
** While the CEA standard[9] lists the FZW event code as "Freeze Warning", Environment Canada refers to it[14] 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[14] 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 Seismic Alert System (also known as SASMEX. The receivers are known as Seismic Alert Radio, and the system known as SARMEX).[15] EQW is referred as "Alerta Sísmica", while VOW is referred to as "Alerta Volcánica".[16] 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.[17]
Internal use only:
Receiver decoders that comply to the CEA standard[9] 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[10] these event codes as being for "internal use only", and not for display. Environment Canada lists[14] these messages as "Administrative Bulletins".
Event Code U.S. Type CAN. Type Event Description Event Level
TXB O2 AB Transmitter backup on ADV
TXF O2 AB Transmitter carrier off ADV
TXO O2 AB Transmitter carrier on ADV
TXP O2 AB Transmitter primary on ADV
Future implementation:
The following codes are part of the CEA standard[9] for receiver decoders, but are not listed as being in use by any agencies in the United States. Environment Canada lists[14] 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
BHW NI FI Biological Hazard Warning WRN
BWW NI FI Boil Water Warning WRN
CHW NI FI Chemical Hazard Warning WRN
CWW NI FI Contaminated Water Warning WRN
DBA NI FI Dam Watch WCH
DBW NI FI Dam Break Warning WRN
DEW NI FI Contagious Disease Warning WRN
EVA NI FI Evacuation Watch WCH
FCW NI FI Food Contamination Warning WRN
IBW NI FI Iceberg Warning WRN
IFW NI FI Industrial Fire Warning WRN
LSW NI FI Landslide Warning WRN
POS NI FI Power Outage Statement ADV
WFA NI FI Wild Fire Watch WCH
WFW NI FI Wild Fire Warning WRN
Future Proposal:
The following codes are not part of the CEA standard for receiver decoders, but are not listed as being in use by any agencies in the United States. The National Weather Service has requested the FCC to create and adopt these codes for future implementation.[18]
Event Code U.S. Type CAN. Type Event Description Event Level
EWW NI N/A Extreme Wind Warning WRN
SSA NI N/A Storm Surge Watch WCH
SSW NI N/A Storm Surge Warning WRN

The FCC established naming conventions for EAS event codes. The third letter of the code must be one of the following.[19]

Third Letter of Event Code Category Description
W Warning An 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.
A Watch Meets the classification of a warning, but either the onset time, probability of occurrence, or location is uncertain.
E Emergency An 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.
S Statement A 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.[10]

SAME 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. It 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. (Examples given: If a person were to live in Irving, Texas, he or she would program a FIPS code for Dallas County. However, if he or she needs to be in the 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 50 miles from the transmitters.[20]

SAME in popular culture

See also

Notes

  1. ↑ A discontinued RadioShack model, the 12-521 (still sold in some locations) and its also discontinued predecessor, the 12-262, in particular were a notable example of this; it was completely normal for them to go off at the first SAME blast, although on these models it was immediate. Their newest successor, the 12-991, has eliminated this quirk.

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 – Metro Skywarn (accessed August 20, 2009)
  7. ↑ 47CFR11.31(d)
  8. ↑ http://www.gpo.gov/fdsys/pkg/CFR-2010-title47-vol1/xml/CFR-2010-title47-vol1-sec11-31.xml
  9. 1 2 3 4 Consumer Electronics Association (CEA) Technology Standard "CEA-2009-B (ANSI)", November 2010, accessed January 11, 2014.
  10. 1 2 3 http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-02-64A1.pdf
  11. ↑ 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
  12. 1 2 Emergency Action Notifications (EAN) and Emergency Action Terminations (EAN) are implemented on some Pacific Northwest NWR Stations. These stations are connected to 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.
  13. ↑ 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
  14. 1 2 3 4 Environment Canada – Weather and Meteorology – "SAME Event Codes"
  15. ↑ http://www.cires.org.mx/sarmex_es.php
  16. ↑ https://www.youtube.com/watch?v=Ogv9gs6-asA
  17. ↑ https://www.youtube.com/watch?v=oG8ZEbU3WYE
  18. ↑ http://blog.sbe.org/2015/07/14/fcc-issues-nprm-to-propose-new-eas-event-codes/
  19. ↑ National Weather Service , accessed September 22, 2012.
  20. ↑ NWR Specific Area Message Encoding (SAME), http://www.nws.noaa.gov/nwr/nwrsame.htm
  21. ↑ Knowing Movie Trailer #2 – Internet Movie Database (accessed July 8, 2009)

External links

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