Text description

Text description – (addressed)

 

Parameter No of bits 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.

0 – 3

0 = default

3 = do not repeat anymore
Source ID

30

 MMSI number of source station.
Sequence Number

2

 0 – 3; refer to § 5.3.1, Annex 2 of ITU-R M.1371-3.
Destination ID

30

 MMSI number of destination station.
Retransmit Flag

1

 Retransmit Flag should be set upon retransmission.

0 = no retransmission = default

1 = retransmitted
Spare

1

 Not used. Set to zero.
IAI

16

 DAC = 001; FI = 30

(See Rec. ITU-R M.1371-3, Annex 5, § 2.1.
Message Linkage ID

10

 Used to link the Text Description message with a main message. The Connection ID and source MMSI MID uniquely identifies the main message.

1 – 1,023

0 = not available = default
Text String

6 – 930

 Free text 1 – 155 characters 6-bits ASCII). If applicable, recommended to use IMO Standard Marine Communication Phrase (SMCP) (see IMO A.918(22)).  Number of slots used should be minimized, refer to Table 14.4.
Spare

0

 Not used. Set to zero.
Total

104 – 1028

 Occupies 1 – 5 slots (see Table 14.4).

 

Table 14.4

Number of slots if sent as an addressed message

 

Number of characters in the message 1-6 7-43 44-81 82-118 119-155
Number of slots used 1 2 3 4 5