Digital Alert Systems DASDEC-II MANUAL - Manual (Page 169)

Digital Alert Systems: DASDEC User Manual
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EAS Protocol
The DASDEC II encodes the EAS messages per FCC rules for the EAS protocol. The EAS protocol from the FCC is described
as follows (printed directly from the FCC ruling).
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 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 1 or 0) 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.
____________________________________________________________
[PREAMBLE]ZCZC-ORG-EEE-PSSCCC+TTTT-JJJHHMM-LLLLLLLL-
(one second pause)
[PREAMBLE]ZCZC-ORG-EEE-PSSCCC+TTTT-JJJHHMM-LLLLLLLL-
(one second pause)
[PREAMBLE]ZCZC-ORG-EEE-PSSCCC+TTTT-JJJHHMM-LLLLLLLL-
(At least a one second pause)
(Transmission of 8 to 25 seconds of Attention Signal)
(Transmission of audio, video or text messages)
(at least a one second pause)
[PREAMBLE]NNNN
(One second pause) [PREAMBLE]NNNN
(One second pause) [PREAMBLE]NNNN
(At least one second pause)
____________________________________________________________
[PREAMBLE] This is a consecutive string of bits (sixteen bytes of AB hexadecimal [8 bit byte 10101011]) sent to clear the
system, set AGC and set asynchronous decoder clocking cycles. The preamble must be transmitted before each header and
End Of Message code.
ZCZC- This is the identifier, sent as ASCII characters ZCZC to indicate the start of ASCII code.
ORG- This is the Originator code and indicates who originally initiated the activation of the EAS. These codes are specified in
paragraph (d) of this section.
EEE- This is the Event code and indicates the nature of the EAS activation. The codes are specified in paragraph (e) of this
section. The Event codes must be compatible with the codes used by the NWS Weather Radio Specific Area Message
Encoder (WRSAME).
PSSCCC- This is the Location code and indicates the geographic area affected by the EAS alert. There may be 31 Location
codes in an EAS alert. The Location code uses the Federal Information Processing Standard (FIPS) numbers as described by
the U.S. Department of Commerce in National Institute of Standards and Technology publication FIPS PUB 6-4. Each state is
assigned an SS number as specified in paragraph (f) of this section. Each county and some cities are assigned a CCC
number. A CCC number of 000 refers to an entire State or Territory. P defines county subdivisions as follows: 0 = all or an
unspecified portion of a county, 1 = Northwest, 2 = North, 3 = Northeast, 4 = West, 5 = Central, 6 = East, 7 = Southwest, 8 =
South, 9 = Southeast. Other numbers may be designated later for special applications. The use of county subdivisions will
probably be rare and generally for oddly shaped or unusually large counties. Any subdivisions must be defined and agreed to
by the local officials prior to use.