Signalling by Morse Code
Morse symbols
Alphabet
Numerals
Procedure Signals
Parts of a signal made by flashing
The call. It consists of the general call or the identity signal of the station to be called. It is answered by the answering signal.
The identity. The transmitting station makes βDEβ followed by its identity signal or name. This will be repeated back by the receiving station, which then signals its own identity signal or name. This will also be repeated back by the transmitting station.
The text. This consists of plain language or code groups. When code groups are to be used they should be preceded by the signal βYUβ. Words of plain language may also be in the text, when the signal includes names, places, etc. Receipt of each word or group is acknowledged by βTβ.
The ending. It consists of the ending signal βARβ which is answered by βRβ.
If the entire text is in plain language the same procedure is to be followed. The call and identity may be omitted when two stations have established communications and have already exchanged signals.
Procedure for sending a message to an unknown ship in Plain language or in code
The General Call signal (including call to an unknown station):
βAA AA AAβ etc. is made to attract the attention when wishing to signal to all stations within visual signaling distance or to a station whose name or identity is not known.
The call is continued until the station addresses.
Once the station signaled to has answered by signaling:
The Answering signal βTTTTβ etc. is made to answer the call and it is to be continued until the transmitting station ceases to make the call.
The transmission starts with the signal βDEβ followed by the name or identity signal of the transmitting station.
If the text is in plain language then the code βYUβ need not be used, but if the message in plain text does contain codes then the code βYUβ has to be transmitted at the beginning of the text message.
After each word or group of words is transmitted the receiving station should signal βTβ, meaning that the word or group has been received.
The βrepeatβ signal
If the receiving station has not received a part of the message then it would send a signal βRPTβ meaning REPEAT WHAT YOU HAVE SENT.
The repetition signals AA, AB, WA, WB and BN
If only a part of the message has not been received properly then it would send as follows:
RPT AA: Repeat all after
RPT AB: Repeat all before
RPT WA: Repeat word after
RPT WB: Repeat word before
RPT BN: Repeat word between
Example:
βRepeat all before group Kilogrammesβ β RPT AB Kilogrammes
βRepeat all between words βboatsβ and βsurvivorsββ β RPT BN boats and survivors
The transmitting station on completing of transmission may send the signal RPT and then commence re-transmitting the entire message.
If however the transmitting station transmits RPT at the end of its transmission and then does not re-transmit then it would mean that it is requesting the receiving station to repeat the entire transmission of what it has received.
The βeraseβ signal when sending or receiving
The Erase signal βEEEEEβ (group of 5 Eβs): is used to indicate that the last group or word was signaled incorrectly. It is to be answered with the erase signal. When answered, the transmitting station will repeat the last word or group, which was incorrectly signaled, and then proceed with the remainder of the transmission.
Important:
If the receiving station receives the message correctly but is unable to understand what has been sent, then it would send the signal by code (ZL) for it to mean, βyour signal has been received but not understoodβ.
A correctly received REPETITION is acknowledged by the signal βOKβ. The same signal may be used as an affirmative (YES) answer to a question (βIt is correctβ).
The Ending signal βARβ is used in all cases to indicate the end of a signal or the end of the transmission. The receiving station answers with the signal βRβ (βReceivedβ or βI have received your last signalβ).
If the transmitting station sends the signal βCSβ it means that it is requesting the name or identity signal of the receiving station.
Use of the waiting signal AS
The signal βASβ is used both as a waiting signal as well as a period signal to separate groups of words.
If the signal βASβ is made independently or after the end of a signal then it means that the other station must wait for further communications.
If the signal βASβ is inserted between word groups then it means that it is being used as a separator between the groups of words.
The use of the procedure signals C, N (or NO), RQ
The signal βCβ should be used to indicate an affirmative statement or an affirmative reply to an interrogative signal. Meaning, it is used when stating in the positive by the transmitting station or when answering positively to a statement by a receiving station.
The signal βRQβ should be used to indicate a question.
For a negative reply to an interrogative signal or for a negative statement, the signal βNβ should be used.
Note: When the signals βNβ or βRQβ are used to change an affirmative signal into a negative statement or into a question, respectively, they should be transmitted after the main signal.
Example:
To transmit the following:
βBoat is not coming to youβ β CY N
βIs boat on board?β β CW RQ
Important: The signals βCβ, βNβ and βRQβ cannot be used together with single letter signals.
The meaning and use of YU, YV, YZ
YU β I am going to communicate with your station by means of the International Code of Signals
YV β The groups which follow are from the International Code of Signals.
YV 1 β The groups which follow are from the local code
YZ β The words which follow are in plain language.
Recommendations on sound signaling
Owing to the nature of the apparatus used (whistle, siren, fog-horn, etc.) sound signaling is necessarily slow. Moreover the misuse of sound signaling is of a nature to create serious confusion at sea. Sound signaling in fog should therefore be reduced to a minimum. Signals other than the single letter signals should be used only in extreme emergency and never in frequented navigational waters.
The signals should be made slowly and clearly. They may be repeated, if necessary but at sufficiently long intervals to ensure that no confusion can arise and that one-letter signals cannot be mistaken as two β letter groups.
Masters are reminded that the one-letter signals of the Code, which are marked with an (*), when made by sound, may only be made in compliance with the requirements of the International Regulationsβ for Preventing Collisions at Sea. Reference is also made to the single β letter signals provided for exclusive use between an ice- breaker and assisted vessels.
Singleβletter signals in addition to the single letter signals
International Regulations for Preventing Collisions at sea
One short blast to mean βI am altering my course to starboardβ;
A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blast. Such signal shall be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.
Written by Capt. Jayant Roy