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1.3 Message Format
For automatic identification of messages, each message starts with eight control characters,
called "Header codes".
The first four characters are always "ZCZC" and common to all messages. This part is used for
message synchronization. The latter four characters are designated as b1, b2, b3 and b4 to
indicate origin, category and serial number of the message.
Character b1 is the identification letter of the NAVTEX station; "A" to "Z". Character b2 indicates
the type of message, "A" to "Z", as listed below. Character b3 and b4 indicate the serial number
of the message. The serial numbers are counted up from "01" to "99", and start from "01" again.
Number "00" is specially reserved for important emergency messages, such as a search and
rescue (SAR) message.
The end of each message is indicated by "NNNN" (four successive N's).
General message format is summarized below.
Start code
(sync)
[Type of message (category)]
A:
Navigational warning
B:
Meteorological warning
C:
Ice report
D:
Search and rescue information/
piracy and armed robbery
E:
Meteorological forecast
F:
Pilot message
G:
DECCA message
H:
LORAN-C message
1-2
Header code
ZCZC b1 b2 b3 b4
Serial number
"00":
"01" - "99": Normal message
Type of message
"A" - "Z"
(See the list below.)
Station ID
"A" - "Z"
main message
Main message
Termination code
Emergency message
I:
OMEGA message
J:
Differential OMEGA message
K:
Other electronic navigational aid
system message
L:
Navigational warning (additional)
M to U: Reserve-presently not used
V:
Notice to Fishermen (U. S. only)
W to Y Reserve-presently not used
Z:
QRU (no message on hand)
NNNN
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