Message Format - Furuno NX-700A Operator's Manual

1. PRINCIPLE OF NAVTEX SYSTEM
1.3

Message Format

For automatic identification of messages, each message starts with nine control
characters, called "Header codes".
The first five characters are always "ZCZC_" and common to all messages. This
part is used for message synchronization. The latter four characters are
designed as b1, b2, b3 and b4 indicate origin, category and serial number of the
message.
Character B1 is the identification letter of the Navtex station "A" thru "Z".
Character B2 indicates the type of message. "A" thru "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 starts 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.
ZCZC
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
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
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
Termination code