Specific Area Message Encoding
Specific Area Message Encoding (SAME) is the protocol used to encode the Emergency Alert System (EAS) and NOAA Weather Radio's SAME Public Warning System in the U.S. and Weatheradio Canada in Canada.
History
From the 1960s to the 1980s, a special feature of the NOAA Weather Radio system was the transmission of a single tone at 1050 Hz 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 has served NOAA Weather Radio well, there were many drawbacks: without staff at media facilities to manually evaluate the need to rebroadcast a Weather Radio 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 that type of 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.
In 1985, the National Weather Service forecast offices began experimenting with putting 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 Weather Radio messages. The NWS started implementing SAME on the full NOAA Weather Radio system in 1988. The SAME technique was later adopted by the FCC in 1997[1] for regular broadcasters on radio, television, and cable, as well as by Environment Canada in 2004[2] for its Weatheradio Canada service. Much like the original EBS alert tone, this produces a distinct sound which is easily recognized by most individuals due to its use in weekly and monthly broadcast tests, and in weather emergencies. 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")[3] just before the attention signal is sent out and at the conclusion of the voice message.[4]
Functionality
In the SAME system, messages are constructed in four parts, the first and last of which are digital. The first part is a header message, which 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 go off after hearing only one out of the three with a significant delay. 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.
The header is an 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.
The text of the header code is a fixed format of [Preamble]ZCZC-org-eee(-pssccc {up to 31 })+tttt-jjjhhmm-llllllll:
- 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
- org: Originator code; programmed per unit when put into operation
- EAN – Emergency Action Notification Network
- President or other authorized national officials. Shall be used starting November 9, 2011 for the national test[5]
- 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
- Formerly Broadcast Station or Cable System.
- Broadcasters. Generally only used with test messages.
- EAN – Emergency Action Notification Network
- eee: Event code; programmed at time of event
- pssccc: Location codes (up to 31 locations); 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.[6]
- In the United States, the remaining five digits are the FIPS state code (ss) and FIPS county code (ccc). The entire state may be specified by using county number 000.
- In Canada, all six digits specify the 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.
- 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, which will purge the warning after the message has been received. However, this is not typical, and FCC guidelines normally suggest a minimum 15 minute 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.
- 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 24-hour hours and minutes, in UTC, with leading zeros
- 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; 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 breakdown
An EAS message contains these elements, in this transmitted sequence:
- Header.
- 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.
- Message — audio, video image or video text.
- 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 1963 when they were part of the EAS' predecessor, the Emergency Broadcast System.
Event codes
There are roughly 80 different event codes that are currently used in EAS and are part of the voluntary Consumer Electronics Association (CEA) standard[7] for SAME protocol receiver decoder units. Originally, all but the first six of these were 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. Furthermore, the creation and evolution of a voluntary standard by the CEA in December 2003 has provided participating manufacturers of receivers a single definitive reference to use when designing and programming receivers.
| USA type key | CAN 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[8][9] | RT | Required test | WRN | Warning |
| NI | Not implemented | FI | For future implementation | TEST | Test |
| TS | Testing for Implementation | ||||
- Currently Implemented:
- The following event codes are currently implemented by agencies in the United States and/or Canada.
-
Event Code U.S. Type CAN. Type Event Description Event Level ADR O1 AB Administrative Message ADV AVA O2 FI Avalanche Watch WCH AVW O2 FI Avalanche Warning WRN BZW O1 CI Blizzard Warning WRN CAE O2 FI Child Abduction Emergency ADV CDW O2 FI Civil Danger Warning WRN CEM O1 FI Civil Emergency Message WRN CFA O2 FI Coastal Flood Watch WCH CFW O2 FI Coastal Flood Warning WRN DMO O1 AB Demonstration Message TEST DSW O2 CI Dust Storm Warning WRN EAN M FI Emergency Action Notification (Begins a nationwide EAS activation) WRN EAT M FI Emergency Action Termination (Ends a national activation) ADV EQW O2 FI Earthquake Warning WRN EVI O1 FI Evacuation Immediate WRN FFA O1 FI Flash Flood Watch WCH FFS O1 FI Flash Flood Statement ADV FFW O1 FI Flash Flood Warning WRN FLA O1 FI Flood Watch WCH FLS O1 FI Flood Statement ADV FLW O1 FI Flood Warning WRN FRW O2 FI Fire Warning WRN FSW NI CI Flash Freeze Warning WRN FZW NI CI Freeze Warning (in Canada, 'Frost Warning' - See note below ** ) WRN HLS O1 FI Hurricane Local Statement ADV HMW O2 FI Hazardous Materials Warning WRN HUA O1 CI Hurricane Watch WCH HUW O1 CI Hurricane Warning WRN HWA O1 FI High Wind Watch WCH HWW O1 CI High Wind Warning WRN LAE O2 FI Local Area Emergency ADV LEW O2 FI Law Enforcement Warning WRN NAT NI AB National Audible Test TEST NIC M AB National Information Center Statement (Used to follow up an EAN) ADV NMN O2 AB Network Message Notification ADV NPT M AB National Periodic Test TEST NST NI AB National Silent Test TEST NUW O2 FI Nuclear Power Plant Warning WRN RHW O2 FI Radiological Hazard Warning WRN RMT M RT Required Monthly Test TEST RWT M RT Required Weekly Test TEST SMW O2 TS Special Marine Warning WRN SPS O1 FI Special Weather Statement ADV SPW O2 FI Shelter In-place Warning WRN SVA O1 CI Severe Thunderstorm Watch WCH SVR O1 CI Severe Thunderstorm Warning WRN SVS O1 TS Severe Weather Statement (U.S., CAN) ADV TOA O1 CI Tornado Watch WCH TOE O2 FI 911 Telephone Outage Emergency ADV TOR O1 CI Tornado Warning WRN TRA O2 CI Tropical Storm Watch WCH TRW O2 CI Tropical Storm Warning WRN TSA O1 TS Tsunami Watch WCH TSW O1 TS Tsunami Warning WRN VOW O2 FI Volcano Warning WRN WSA O1 CI Winter Storm Watch WCH WSW O1 CI Winter Storm Warning (Canada, see note below † ) WRN ??A O2 CI Unrecognized Watch WCH ??E O2 CI Unrecognized Emergency ADV ??S O2 CI Unrecognized Statement ADV ??W O2 CI Unrecognized Warning WRN
- ** While the CEA standard[7] lists the FZW event code as "Freeze Warning", Environment Canada refers to it[10] 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[10] 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
- Internal Use Only:
- Receiver decoders that comply to the CEA standard[7] 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[8] these event codes as being for "internal use only", and not for display. Environment Canada lists[10] 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[7] for receiver decoders, but are not listed as currently being in use by any agencies in the United States. Environment Canada lists[10] these codes as being "for future implementation".
-
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 Land Slide Warning WRN POS NI FI Power Outage Statement ADV WFA NI FI Wild Fire Watch WCH WFW NI FI Wild Fire Warning WRN
The FCC established naming conventions for EAS event codes. The third letter of the code must be one of the following.[11]
-
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.[8]
SAME on weather radio receivers
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.[12]
SAME in popular culture
- The SAME EOM (end of message) tone was heard in the movie trailer for Knowing and in the series Jericho where its familiar emergency use and its increasing cadence create a sense of foreboding.[13] It has been recently used in the movie trailer for "Olympus Has Fallen" and "The Purge".
See also
- Common Alerting Protocol (CAP) – A SAME-compatible digital format for multi-system warning coordination.
References
- ^ NOAA Weather Radio - Watches, Warnings and Tones/Alarms – National Weather Service in Philadelphia/Mount Holly (accessed October 1, 2009)
- ^ [1] – The Green Lane: (Backgrounder) – Weatheradio Network (accessed Dec. 5, 2011)
- ^ http://www.wsab.org/eas/eas_meeting_minutes_jan06.html
- ^ WRSAME – Weather Radio Specific Area Message Encoder – Metro Skywarn (accessed August 20, 2009)
- ^ http://www.fema.gov/emergency/ipaws/eas_info.shtm
- ^ http://www.gpo.gov/fdsys/pkg/CFR-2010-title47-vol1/xml/CFR-2010-title47-vol1-sec11-31.xml
- ^ a b c d Consumer Electronics Association (CEA) Technology Standard "CEA-2009-B (ANSI)", November 2010, accessed May 10, 2011.[dead link]
- ^ a b c http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-02-64A1.pdf
- ^ 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
- ^ a b c d Environment Canada – Weather and Meteorology – "SAME Event Codes"
- ^ National Weather Service [2], accessed September 22, 2012.
- ^ NWR Specific Area Message Encoding (SAME), http://www.nws.noaa.gov/nwr/nwrsame.htm
- ^ Knowing Movie Trailer #2 – Internet Movie Database (accessed July 8, 2009)
- National Weather Service (February 12, 2007), NOAA Weather Radio (NWR) All Hazards Specific Area Message Encoding (SAME), National Weather Service Instruction, 10-1712, National Oceanic & Atmospheric Administration
