Text telegram using 6-bit ASCII

Introduction/Additional information:

This IFM should be used by a ship or base station to send 6-bit ASCII text telegram to other AIS stations. The text telegram can be sent with either binary message 6 or 8. The acknowledge required flag should not be set when using the broadcast message 8.Replaced by ITU-R.M.1371-3

Message number:
Number of slots (max):
Permitted as from:
Not to be used after:
International function message 0 using Message 6, addressed binary message
Parameter Number 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. See § 4.6.1, Annex 2; 0-3; 0 = default;
3 = do not repeat any more
Source ID 30 MMSI number of source station
Sequence number 2 0-3; see § 5.3.1, Annex 2
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. Should be zero
DAC 1 International DAC = 110 = 00000000012
FI 0 Function identifier = 010 = 0000002
Acknowledge required flag 1 1 = reply is required
0 = reply is not required
Message sequence number 11 Sequence number to be incremented by the application.
All zeros indicates that sequence numbers are not being used
Text message 924 6-bit ASCII as defined in Table 14. When using this IFM, the number of slots used for transmission should be minimized taking into account the table below
Spare bits N Formula for inserting for spare bits
Total number of application data bits 936

The following table gives the number of 6-bit-ASCII characters, so that the whole message fits into a given number of slots. It is recommended that any application minimizes the use of slots by limiting the number of characters to the numbers given, if possible:

Number of slots Maximum number of 6-bit ASCII characters
Addressed binary message, 06 Broadcast binary
1                    8                  14
2                  46                  51
3                  83                  88
4                120                126
5                158                163