4. General Communication Knowledge 

When you need to spell a word, only the standardized spelling table should be used. 

In shore-to-ship and ship-to-shore communication or radio communication in general, the following eight Message Markers may be used: 

(i) Instruction 

(ii) Advice 

(iii) Warning 

(iv) Information 

(v) Question 

(vi) Answer 

(vii) Request 

(viii) Intention

• When the answer to a question is in the affirmative, say: 

 "Yes ...." followed by the appropriate phrase in full. 

• When the answer to a question is in the negative, say: 

"No ..." followed by the appropriate phrase in full. 

• When the information requested is not immediately available, say: 

"Stand by" followed by the time interval within which the information will be available. 

• When the information requested cannot be obtained, say: 

     "No information." 

• When an INSTRUCTION (e.g. by a VTS Station, naval vessel or other fully authorized personnel) or an ADVICE is given, respond if in the affirmative: 

          "I will/can … " - followed by the instruction or advice in full; and, 

     if in the negative, respond: 

             "I will not/cannot … " - followed by the instruction or advice in full. 

    Example: "ADVICE. Do not overtake the vessel North of you." 

     Respond: "I will not overtake the vessel North of me."

• Responses to orders and answers to questions of special importance both in  external and on-board communication are given in wording in the phrases concerned.

• MAYDAY ……….to be used to announce a distress message 

• PAN PAN ……….to be used to announce an urgency message 

• SECURITE ………to be used to announce a safety message

• Q: "How do you read (me)?" 

A: "I read you ... 

bad/one with signal strength one (i.e. barely perceptible) 

poor/two with signal strength two (i.e. weak) 

fair/three with signal strength three (i.e. fairly good) 

good/four with signal strength four (i.e. good) 

excellent/five with signal strength five (i.e. very good) 

• When it is advisable to remain on a VHF Channel / frequency, say: 

"Stand by on VHF Channel ... / frequency ... ." 

• When it is accepted to remain on the VHF channel / frequency indicated, say:    "Standing by on VHF Channel ... / frequency ... . " 

• When it is advisable to change to another VHF Channel / frequency, say: 

"Advise (you) change to VHF Channel ... / frequency ..." 

"Advise (you) try VHF Channel ... / frequency... ."

• When the changing of a VHF Channel / frequency is accepted, say: 

"Changing to VHF Channel ... / frequency ... ."

• When a mistake is made in a message, say: 

"Mistake ..." followed by the word: 

"Correction ... " plus the corrected 

Example: "My present speed is 14 knots - mistake. 

Correction, my present speed is 12, one-two, knots." 

"I am/I am not ready to receive your message."

• If any parts of the message are considered sufficiently important to need safeguarding, say: 

"Repeat ... " - followed by the corresponding part of the message. 

Example: "My draft is 12.6 repeat one-two decimal 6 metres." 

"Do not overtake - repeat - do not overtake."

• When a message is not properly heard, say: 

"Say again (please)."

Numbers are to be spoken in separate digits: 

"One-five-zero" for 150 

"Two decimal five or Two point five" for 2.5 

Note: Attention! When rudder angles, e.g. in wheel orders, are given, say: "Fifteen" for 15 or "Twenty" for 20 etc.

• When latitude and longitude are used, these shall be expressed in degrees and minutes (and decimals of a minute if necessary), North or South of the Equator and East or West of Greenwich. 

Example: "WARNING. Dangerous wreck in position 15 degrees 34 minutes North 061 degrees 29 minutes West." 

• When the position is related to a mark, the mark shall be a well-defined charted object. The bearing shall be in the 360 degrees notation from true north and shall be that of the position FROM the mark. 

Example: "Your position bearing 137 degrees from Big Head lighthouse distance 2.4 nautical miles."

The bearing of the mark or vessel concerned is the bearing in the 360 degree notation from north (true north unless otherwise stated), except in the case of relative bearings. 

Bearings may be either FROM the mark or FROM the vessel. 

Examples: "Pilot boat is bearing 215 degrees from you." 

Note: Vessels reporting their position should always quote their bearing FROM the mark, as described in paragraph 11.2 of this section. 

Relative bearings can be expressed in degrees relative to the vessel's head. More frequently this is in relation to the port or starboard bow. 

Example: "Buoy 030 degrees on your port bow." 

(Relative D/F bearings are more commonly expressed in the 360 degree notation.)

Always to be expressed in 360 degree notation from north (true north unless otherwise stated). Whether this is to TO or FROM a mark can be stated. Relative bearings can be expressed in degrees relative to the vessel's head. More frequently this is in relation to the port or starboard bow. 

Example: "Buoy 030 degrees on your port bow." 

(Relative D/F bearings are more commonly expressed in the 360 degree notation.)

To be expressed in nautical miles or cables (tenths of a mile), the unit always to be stated. 

To be expressed in knots: 

-without further notation, meaning speed through the water; or,v"ground speed", meaning speed over the ground. 

Times should be expressed in the 24 hour UTC notation; if local time will be used in ports or harbours it should clearly be stated.

Some words in English have meanings depending on the context in which they appear. 

Misunderstandings frequently occur, especially in VTS communications, and have produced accidents. Such words are:

• The conditionals "may", "might", "should" and "could" 

May 

Do not say: "May I enter the fairway?" 

Say: "QUESTION.Do I have permission to enter the fairway?" 

Do not say: "You may enter the fairway." 

Say: "ANSWER. You have permission to enter the fairway." 

Might 

Do not say: "I might enter the fairway." 

Say: "INTENTION. I will enter the fairway. " 

Should 

Do not say: "You should anchor in anchorage B 3." 

Say: "ADVICE. Anchor in anchorage B 3." 

Could 

Do not say: "You could be running into danger." 

Say: "WARNING. You are running into danger." 

• The word "can" 

The word "can" describes either the possibility or the capability of doing something. In the IMO SMCP the situations where phrases using the word "can" appear make it clear whether a possibility is referred to .In an ambiguous context, however, say, for example: 

"QUESTION. Do I have permission to use the shallow draft fairway at this time?" 

Do not say: "Can I use the shallow draft fairway at this time?" if you are asking for a permission. 

(The same applies to the word "May")