Furuno NX-700A/B 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:	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					L:	navigational warning (additional)
	and armed robbery
E:	meteorological forecast					M to Y: reserved presently not used
F:	pilot message
G:	AIS
H:	LORAN-C message					Z:	QRU (no message on hand)

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