Binary acknowledgement of addressed message 168 S 1 AU AS IN SOTDMA RATDMA ITDMA MOBILE BASE AIS message number. Must be 7 7 Indicated how many times a message has been repeated 0 default do not repeat any more 1 Unique ship identification number (MMSI). Also known as the Source ID 1193046 Not used. Should be set to zero. 0 MMSI destication to ACK 1193001 Sequence ID of the message to be acknowledged 1 MMSI destication to ACK 1193002 Sequence ID of the message to be acknowledged 2 MMSI destication to ACK 1193003 Sequence ID of the message to be acknowledged 3 MMSI destication to ACK 1193004 Sequence ID of the message to be acknowledged 0