INTERCO or International Code of Signals

INTERCO or International Code of Signals is an international system of communication used by seafarers on onboard vessels to convey important information, pertaining to navigation, safety and other operational issues. This is a standardised system which uses various signals and codes that help overcome the communication blockage which arises as seafarers of different nationalities speak different languages.

This system of signals standardises messages in 9 languages including English, Japanese, Norwegian, Russian, Italian, Greek, French, Spanish and German. It does not matter if those sending and receiving the messages speak different languages, as each language comes with a handbook with a corresponding message which is keyed to the same code.

INTERCO is useful when those onboard vessels can hear or see each other. The code also has procedures on how to initiate a call, a message’s formatting etc.

This article will offer a detailed perspective on the International Code of Signals, its history in brief, its importance and how it is used by seafarers and professionals in the maritime industry.

But first, let us understand what maritime signalling is. It is a system of communication between ships at sea or professionals working offshore via radio communication, the use of whistles and hoisting flags.

Along with communication barriers, mobile networks do not work overseas so maritime signalling helps in seamless communication and avoiding errors due to miscommunication. There are different signals to be used in different situations and emergencies that seafarers should know.

Brief History of the International Code of Signals (INTERCO)

Before the International Code of Signals came into being, several naval and private signals were in use, such as the Marryat’s Code in the mid-1850s.

From the early to the mid-1800s, Britain, France and the United States undertook it upon themselves to devise their signalling systems and the British Royal Navy introduced a flag signalling method.

The British Board of Trade drafted the International Code of Signals in 1855, which was published as the Commercial Code in 1857. It offered common signals, mainly using flags for communicating messages like distress, navigation requests and vessel identification.

The need for this code was felt as maritime trade and shipping increased in the 19th century and earlier signalling was restricted to specific regions or nations leading to barriers in communication. With time, this code was revised and new methods of signalling like the use of Morse code were introduced.

After the Second World War, the IMO became active in standardising maritime communication and so the code was further refined to incorporate modern maritime technologies like radio signals while the flag system was retained.

Today, the International Code of Signals is maintained by the IMO which published an edition in 2005. It includes visual signals or flags, sound signals like whistles or horns and radio communication protocols. These signals are recognised universally by all maritime professionals.

Signals Used In INTERCO

Signals can be divided into three categories

Single-letter signals that are important, urgent and common.
Two-letter signals for other messages, followed by a numerical complement sometimes, to supplement the message.
Three-letter signals starting with M which are Medical Signal Codes.

1. Flag Signals (Using Specific Flags)

As the name suggests, flag signals use flags or pennants to convey important information. One or two flags were used to enable communication at a distance before the radio was invented. In Flag hoist signalling, each flag or a combination of flags has a preassigned meaning or code. The INTERCO has a standard set of flags and an associated alphabet for international use and also a set of codes.

Flag Signals are used for

International distress signals, for e.g. using a single flag representing an emergency.
Giving navigational warnings like signalling a ship’s course or location.
Sending Requests for Assistance, e.g. signalling for medical help or for towing a vessel

Every signal can be easily recognised from a distance as the flags are in bright colours and distinct patterns.

2. Morse Code (Through radio or light signals)

A signal lamp also called a Morse lamp or Aldis lamp is a visual signalling device for communicating using flashes, typically using Morse Code. The concept of flashing dots and dashes from a lantern was envisaged by Captain Philip Howard Colomb of the Royal Navy in 1867, though his code was not the same as Morse Code.

In WWI, Germans made use of optical transmitters using Morse code within a range of five miles with red filters.

Today, signal lamps generate a focused pulse of light, by opening and closing shutters in front of the lamp or by using a concave mirror. They are still used on naval ships and in air traffic control towers, in case the radio communication fails.

3. Flag Semaphore

Flag Semaphore is another effective system of communication when the two parties are at a distance from each other. It uses visual signals like flags held in both hands at different positions, disks, paddles, rods etc.

The semaphore system was greatly used in the 19th century and is still used today during underway replenishment at sea and for emergency communication in daylight or by using lighted wands rather than flags at nighttime.

4. Sound Signals (Using a Ship’s horn or whistling)

Sound Signals, including the use of horns or whistles, come under the International Regulations for Preventing Collisions at Sea and may be used in situations when using flag signals is not possible. The use of sound signals is important to avoid ship collisions in bad weather or low visibility at sea and ensure safe navigation.

5. Voice Communication (Through Radio)

Using voice communication via radio is the easiest way to communicate. Several standard maritime communication phrases can be used to convey the message to the crew members of the other ship. This method of communication is convenient and can be used when there is considerable distance between the two parties.

Components of the INTERCO System

The International Code of Signals uses a combination of signal flags, messages and alphabetic codes and has the below-mentioned components.

Alphabetical Code

Every letter of the alphabet is assigned a specific flag which is used individually or in combination to convey messages.

For instance, the flag for letter A is a white and blue flag with vertical stripes, and the flag for letter B is all red.

The 26 Nautical Flags beginning with a new alphabet represent a new message.

For example:

Alpha- “Diver down, keep clear.”
Bravo- ‘I am taking in, discharging, or carrying dangerous goods. ‘
Charlie- “Yes” (confirmation).
Whiskey- ‘I require medical assistance. ‘

Numerical Code

There are 10 numeral pennants from 0 to 9 which help in identifying ships. It is used to distinguish ships with the same or similar names or assist in ship recognition among a fleet of vessels belonging to the same class.

This system also helps convey information like coordinates, time, or speed.

Message Codes

This includes predefined messages used in specific situations, ranging from simple messages like ‘I am disabled and need assistance’ to complex messages, which help convey urgent information quickly.

Special Signals

These indicate specific requirements or operations, such as a vessel engaged in towing or a ship needing medical help.

Group Signals

This includes signals made by flying several flags together, creating a group that depicts a complete message. For eg. ‘I am in distress’ can be signalled by using a combination of flags, each one standing for a part of the message.

Importance of the International Code of Signals

INTERCO establishes a universal form of communication which ensures the safety of seafarers and ships by enabling clear and swift communication between vessels or port authorities from different parts of the world. In emergencies like collisions, medical accidents, groundings etc, accurate signalling can make a big difference in preventing accidents and saving lives.

INTERCO is quite expansive and is not restricted to one form of communication, rather has different modes of signalling ships, shore stations or authorities including the use of flags, torches, radio, whistles etc, so even if one method fails, there are plenty of others.

INTERCO

The International Code of Signals enables consistent interpretation of the codes throughout the shipping industry around the world, boosting maritime security. Ships can communicate emergency plans with each other if needed in case they cannot connect with nearby port authorities while facing maritime threats, accidents or cybersecurity issues.

INTERCO also increases efficiency, and streamlines processes in the maritime industry. It is used for daily operations as well, such as signalling manoeuvring intentions, reporting navigational hazards and providing updates on the status of ships.

Today, INTERCO is usually integrated into navigational and communication systems such as the Global Maritime Distress and Safety System or GMDSS which automate most functions but INTERCO is a vital part of safety drills and emergency procedures.

Challenges in Using INTERCO

Despite being universally used in the maritime industry, INTERCO also has a few limitations.

During rough seas and poor visibility, visual signalling can be difficult to interpret for the other party and even radio signals might be subject to interference.

All seafarers must be adequately trained in using the Code properly to ensure effective communication. Using the wrong code or signal in an emergency can be catastrophic.

Conclusion

INTERCO is an intrinsic part of the maritime industry, without which smooth maritime trade operations across the globe would be impossible. It allows seafarers and maritime professionals in shore stations or ports to effectively and clearly communicate with ships at sea and send help quickly if needed.

By understanding and learning the various methods of signalling, using flags, morse code, radio etc, maritime professionals can enhance emergency preparedness, boost operational efficiency and contribute to a safer maritime environment. This can be done through participating in training exercises regarding INTERCO, ranging from its use in routine operations to emergencies.

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About Author

Zahra is an alumna of Miranda House, University of Delhi. She is an avid writer, possessing immaculate research and editing skills. Author of several academic papers, she has also worked as a freelance writer, producing many technical, creative and marketing pieces. A true aesthete at heart, she loves books a little more than anything else.

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