Sound signals for vessels in restricted visibility (day and night)
| Description | Max period | Signal |
|---|---|---|
| Power under way and making way | every two minutes | |
| Power under way and not making way through water | every two minutes |  |
| • Not under command • Restricted manoeuvring • Constrained by her draught • Sailing ship – not under power • Vessel fishing • Vessel towing or pushing | every two minutes |  |
| Vessel towed – if manned | every two minutes | |
| Pilot vessel on duty– gives normal signals above and may sound four short blasts | | |
| Vessel at anchor (under 100 m in length) BELL rung for five seconds | every minute |  |
| Vessel at anchor (100 m or more in length) BELL rung for five seconds from the bow of the vessel and then – GONG rung five seconds from the aft of the vessel immediately following bell signal | every minute |  |
| Vessel at anchor – may give WARNING of possibility of collision to approaching vessel | | |
| Vessel aground – as at anchor but preceded and followed by three separate and distinct BELL strokes |  | |
| Vessels under 12 m in length may make the appropriate signals given above but, if not, must make some other efficient sound signal every two minutes |