§11.31. EAS protocol.
47 C.F.R. § 11.31
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.
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.
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.
The message may be audio, video or text.
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.
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.
Examples are provided in FCC Public Notices.
The only originator codes are—
[Reserved]
The following Event (EEE) codes are presently authorized—
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.
Notes, amendments, and revision history
Amendments
[59 FR 67092, Dec. 28, 1994, as amended at 60 FR 55999, Nov. 6, 1995; 61 FR 54952, Oct. 23, 1996; 63 FR 29663, June 1, 1998; 67 FR 18508, Apr. 16, 2002; 67 FR 77174, Dec. 17, 2002; 69 FR 72031, Dec. 10, 2004; 70 FR 71033, Nov. 25, 2005; 77 FR 16701, Mar. 22, 2012; 80 FR 37174, June 30, 2015; 81 FR 53043, Aug. 11, 2016; 83 FR 2563, Jan. 18, 2018; 87 FR 67823, Nov. 10, 2022; 89 FR 72737, Sept. 6, 2024; 91 FR 1404, Jan. 14, 2026]
Authority
Authority: 47 U.S.C. 151, 154 (i) and (n), 303(r), 544(g), 606, 1201, and 1206.
Source
Source: 59 FR 67092, Dec. 28, 1994, unless otherwise noted.
Amendments
[59 FR 67092, Dec. 28, 1994, as amended at 60 FR 55999, Nov. 6, 1995; 61 FR 54952, Oct. 23, 1996; 63 FR 29663, June 1, 1998; 67 FR 18508, Apr. 16, 2002; 67 FR 77174, Dec. 17, 2002; 69 FR 72031, Dec. 10, 2004; 70 FR 71033, Nov. 25, 2005; 77 FR 16701, Mar. 22, 2012; 80 FR 37174, June 30, 2015; 81 FR 53043, Aug. 11, 2016; 83 FR 2563, Jan. 18, 2018; 87 FR 67823, Nov. 10, 2022; 89 FR 72737, Sept. 6, 2024; 91 FR 1404, Jan. 14, 2026]