Definitions

special marine warning

Specific Area Message Encoding

Specific Area Message Encoding or SAME is the protocol used to encode the Emergency Alert System in the U.S. for broadcast stations. It was originally created for NOAA Weather Radio by the National Weather Service, and was later adopted by the FCC for regular broadcasters on radio, television, and cable, as well as by Environment Canada for its weather radio service.

Functionality

The system transmits digital tones over normal audio using AFSK, with a 2083.3 Hz mark tone and 1562.5 Hz space tone, lasting 1920 μs (1.92 ms) each. The data is encoded in 7-bit ASCII but uses all 8 bits, with no parity bit and no stop bit ("8-N-0"), at a bitrate of 520.83 bits per second. The least significant bit of each byte is transmitted first, including the preamble. The tones are multiples of the bitrate.

In the SAME system, messages are constructed in four parts, the first and last of which are digital. The first part is the AFSK-encoded header message in 7-bit ASCII text. It is repeated 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. The text of the header code contains:

  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
  2. Information about the originator of the alert:
    • EAN - national authorities, including the President (Emergency Action Notification Network)
    • PEP - national authorities, including the President (Primary Entry Point System)
    • CIV - civil authorities, such as president, governor or local city/county emergency management agency
    • WXR - National Weather Service weatheradio
    • EAS - broadcasters, such as radio & TV stations, or cable TV companies
  3. Event type (see below)
  4. Areas affected (up to 32), designated by FIPS state code and indicating the county (parish in Louisiana, borough or census area in Alaska), but which may be designated for the whole state by using county number 000.
  5. Duration of alert, normally in increments of 15 minutes from time of issue
  6. Exact time of issue, in UTC, without time zone adjustments
  7. Eight-character station callsign identification, with / used instead of - .

Full Message Breakdown

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

  1. Header: (Preamble) ZCZC-org-eee-pssccc-pssccc+tttt-jjjhhmm-llllllll
  2. Attention signal (audio tone for Weatheradio, combined tones for commercial 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.

  • (Preamble): Signal that clears and resets the receiving system; factory-programmed
  • ZCZC: Start of ASCII code; factory-programmed
  • org: Originator code; programmed per unit when put into operation
  • eee: Event code; programmed at time of event
  • pssccc: County-location codes (up to 32 locations); programmed at time of event
    • ss is the state or equivalent water area code
    • ccc is the county/borough/parish, independent city, or equivalent (000 for entire state)
    • p is the part of the county, or 0 for the entire county
  • tttt: Duration the alert is valid (hhmm format); programmed at time of event
  • jjjhhmm: Date and Time-of-Day; encoded automatically, based on settings
    • jjj is the Julian date day of the year, in UTC, with leading zeros
    • hhmm is 24-hour hours and minutes, in UTC, with leading zeros
  • llllllll: Eight-Character ID; programmed per unit when put into operation
    • broadcast station callsign, such as WXXX/FM
    • NWS location, such as KDEN/NWS for Denver, Colorado
  • Attention signal: Sent if any message is included (normally sent with all messages except RWT); must be at least eight seconds long
  • NNNN: End-of-message code (EOM)

Event codes

There are about 80 different event codes currently used in EAS. 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.

Mandatory codes

  1. EAN: Emergency Action Notification (Activates the EAS nationwide)
  2. EAT: Emergency Action Termination (Ends national activation)
  3. NIC: National Information Center statement (Used to distribute National level information after EAT has been sent)
  4. RMT: Required Monthly Test
  5. RWT: Required Weekly Test
  6. NPT: National Periodic Test

Original optional codes

  1. BZW: Blizzard Warning
  2. CEM: Civil emergency Message
  3. CFA: Coastal Flood watch
  4. CFW: Coastal Flood Warning
  5. DMO: Demonstration message
  6. EVI: Evacuation Immediate
  7. FFA: Flash flood Watch
  8. FFS: Flash Flood Statement
  9. FFW: Flash Flood Warning
  10. FLA: Flood watch
  11. FLS: Flood Statement
  12. FLW: Flood Warning
  13. HUA: Hurricane watch
  14. HUW: Hurricane Warning
  15. HWA: High Wind watch
  16. HWW: High Wind Warning
  17. SPS: Special Weather Statement
  18. SVA: Severe thunderstorm watch
  19. SVR: Severe thunderstorm warning
  20. SVS: Severe Weather Statement
  21. TOA: Tornado watch
  22. TOR: Tornado warning
  23. TRA: Tropical storm watch
  24. TRW: Tropical Storm Warning

Optional codes added in 2002

  1. ADR: Administrative message
  2. AVA: Avalanche watch
  3. AVW: Avalanche Warning
  4. BHW: Biological Hazard Warning
  5. BWW: Boil Water Warning
  6. CAE: Child Abduction Emergency
  7. CDW: Civil Danger Warning
  8. CHW: Chemical Hazard Warning
  9. CWW: Contaminated Water Warning
  10. DBA: Dam Break watch
  11. DBW: Dam Break Warning
  12. DEW: Contagious disease Warning
  13. DSW: Dust storm Warning
  14. EQW: Earthquake Warning
  15. EVA: Evacuation watch
  16. FCW: Food Contamination Warning
  17. FRW: Fire Warning
  18. FSW: Flash Freeze Warning
  19. FZW: Freeze Warning
  20. HLS: Hurricane Local Statement
  21. HMW: Hazardous Materials Warning
  22. IBW: Iceberg Warning
  23. IFW: Industrial Fire Warning
  24. LAE: Local Area Emergency
  25. LEW: Law Enforcement Warning
  26. LSW: Land Slide Warning
  27. NAT: National Audible Test
  28. NMN: Network Message motif
  29. NST: National Silent Test
  30. NUW: Nuclear Plant Warning
  31. POS: Power Outage Statement
  32. RHW: Radiological Hazard Warning
  33. SMW: Special Marine Warning
  34. SPW: Shelter in Place Warning
  35. TOE: 911 Telephone Outage Emergency
  36. TSA: Tsunami watch
  37. TSW: Tsunami Warning
  38. TXB: Transmitter Backup on
  39. TXF: Transmitter carrier off
  40. TXO: Transmitter carrier on
  41. TXP: Transmitter Primary on
  42. VOW: Volcano Warning
  43. WFA: Wild Fire watch
  44. WFW: Wild Fire Warning
  45. WSA: Winter storm watch
  46. WSW: Winter Storm Warning
  47. ??A: Unrecognized Watch
  48. ??E: Unrecognized Emergency
  49. ??S: Unrecognized Statement
  50. ??W: Unrecognized Warning

See also

External links

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