Collision alarm
| Parameter | Number of bits | Description |
| Message ID | 6 | Identifier for this message 6; always 6. |
| Repeat Indicator | 2 | Used by the repeater to indicate how many times a message has been repeated. 0 – 3; default = 0; 3 = do not repeat any more. |
| Source ID | 30 | MMSI number of source station |
| Sequence Number | 2 | 0 – 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. Should be zero |
| DAC | 10 | Destination Area Code. Default: 421 |
| FI | 6 | Function Identifier Default: 16 |
| Sub Function Identifier | 16 | Default: 0 |
| Direction | 12 | 0 -359 (deg)
Direction to the ship which sent warning. |
| Distance | 10 | 0 – 127 (1/10 nm)
Distance to the ship which sent warning. |
| Warning Level | 2 | 0 – 3
0:Release from caution
|
| Arrival Time | 8 | 0 – 256 (1/10 minutes)
Estimated arrival time to the future position a collision. |
| Spare | 4 | For future use. Should be zero. |
| TOTAL OF BITS. | 136 | Occupies 1 slot. |