Safety related broadcast message

msg_ID: 
14
Description: 
Safety related data for broadcast communication
Priority: 
2
Access scheme: 
RATDMA
ITDMA
FATDMA
Communication state: 
N/A
Transmitted by: 
Mobile station
Base station

The safety related broadcast message could be variable in length, based on the amount of safety related text. The length should vary between 1 and 5 slots.

TABLE 63
Parameter Number of bits Description
Message ID 6 Identifier for Message 14; always 14.
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 of message
Spare 2 Not used. Should be set to zero. Reserved for future use
Safety related text Maximum 968 6-bit ASCII as defined in Table 47
Maximum number of bits Maximum 1 008 Occupies up to 3 slots, or up to 5 slots when able to use FATDMA reservations.
For Class B “SO” mobile AIS stations the length of the message should not exceed 3 slots
For Class B “CS” mobile AIS stations the length of the message should not exceed 1 slot
 

 
Additional bit stuffing will be required for this message type. For details refer to transport layer, § 5.2.1, Annex 2.
Table 64 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 6-bit ASCII characters
1 16
2 53
3 90
4 128
5 161
 

 
These numbers also take bit stuffing into account.
The AIS-SART should use Message 14, and the safety related text should be:
1)          For the active SART, the text should be “SART ACTIVE”.
2)          For the SART test mode, the text should be “SART TEST”.
3)          For the active MOB, the text should be “MOB ACTIVE”.
4)          For the MOB test mode, the text should be “MOB TEST”.
5)          For the active EPIRB, the text should be “EPIRB ACTIVE”.
6)          For the EPIRB test mode, the text should be “EPIRB TEST”.