Parameter

Bit

Description

Message ID

6

Identifier for Message 6; always 6

Repeat Indicator

2

Used by the repeater to indicate how many times a message has been repeated.
Default = 0; 3 = do not repeat any more

Source ID

30

MMSI number

Sequence Number

2

0 – 3

Destination ID

30

MMSI number

Retransmit Flag

1

Retransmit Flag should be set upon retransmission: 0 = no retransmission = default; 1 = retransmitted.

Spare

1

not used, should be set to zero, reserved for future use

Binary data

Application Identifier

16

DAC = 200, FI = 44

Version indicator

3

The version number of the message default = 0, rest for future use

UN country code

12

2*6 Bit characters, digits 1 and 2 of the ISRS code

Fairway section number

17

bit coded numerical value 1-99999, 0=unknown, rest not used, digits 6 to 10 of the ISRS code

Object code

30

5*6 Bit characters

Fairway hectometre

17

bit coded numerical value 1-99999, 0=unknown, rest not used, digits 16 to 20 of the ISRS code

Spare

1

reserved; should be set to 0

Text

222 -

450

37 to 75 x 6-bit ASCII as defined in ITU-R M.1371

Spare

max 6

Not used for data and should be set to zero. Spare bits are needed to maintain byte boundaries.

NOTE 1 – When a 6 or 7-bit spare is needed to satisfy the 8-bit byte boundary rule, the 6-bit spare will be interpreted as a valid 6 bit character (all zeros is the “@” character).

Total

occupies 2 to 3 slots