User's Manual

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, 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 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: OMEGA message
B: Meteorological warning J: Differential OMEGA 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 M to U: Reserve-presently not used
F: Pilot message V: Notice to Fishermen (U. S. only)
G: DECCA message W to Y: Reserve-presently not used
H: LORAN-C message Z: QRU (no message on hand)