Furuno NX-700A/B - Manual (Page 14)

1. PRINCIPLE OF NAVTEX SYSTEM
1-2
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.
The end of each message is indicated by “NNNN” (four successive N’s).
General message format is summarized below.
ZCZC B1 B2 B3 B4 main message NNNN
Header code
Start code
(sync) Main message Termination code
Serial number
"00": Emergency message
"01" - "99": Normal message
Type of message
"A" - "Z"
(See the list below.)
Station ID
"A" - "Z"
[Type of message (category)]
A: navigational warning I: reserved presently not used
B: meteorological warning J: SATNAV message
C: ice report K: other electronic navigational
aid system message
D: search and rescue information/piracy
and armed robbery L: navigational warning (additional)
E: meteorological forecast
F: pilot message
G: AIS
M to Y: reserved presently not used
H: LORAN-C message Z: QRU (no message on hand)