Sound Signals

  • Short blast: A blast of about 1 second’s duration.
  • Prolonged blast: A blast of from 4 to 5 second’s duration


Altering course to port.

Altering course to starboard.

Intentions are not understood.


A vessel being towed if manned. At least every two minutes. Sounded by the last vessel in tow immediately after the towing vessel’s signal

A vessel at anchor Morse “R” to warn the approaching vessel

Engines are running astern

Not under command. Restricted in ability to manoeuvre. Constrained by draught. A vessel engaged in fishing. Vessel towing or pushing


Power Vessel Stopped. Two long blasts at intervals of not more than 2 minutes


Power vessel underway., one long blast at intervals of not more than 2 minutes. also when approaching a bend in a fairway where the view of other vessels may be obscured.