Furuno NX-700B manual Message Format, Nnnn

1. PRINCIPLE OF NAVTEX SYSTEM

1.3Message 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.

		Header code
						main message			NNNN
	ZCZC B1 B2 B3 B4
	Start code					Main message		Termination code
	(sync)			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:	Spare
B:	Meteorological warning					J:	SATNAV message
C:	Ice report					K:	Other electronic navigational aid
							system message

D:	Search and rescue information/pirate	L:
	attack warnings
E:	Meteorological forecast	V to Y
F:	Pilot message
G:	AIS
H:	LORAN message	Z:

Navigational warning (addition to “A”)

Special services allocation by the NAVTEX Co-ordinating Panel

QRU (no message on hand)

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