Remarkable advances in technology mean that sailors are no longer isolated from the rest of the world while at sea

Throughout history sailors would have to go many months without news from home but satellite technology now enables today’s seafarers to be in constant contact.

Fire was the first method of signalling between land and sea and the earliest known lighthouse using a fire beacon was built around 280BC in Alexandria, Egypt. This tower, now listed as one of the Seven Wonders of the Ancient World, is said to have stood 140m tall.

Lighthouses
In Britain the Eddystone Lighthouse, completed in 1698, was the first offshore lighthouse. It was built 13 miles off Plymouth to warn sailors of a treacherous group of rocks in the approach to the English Channel.

Today, the fourth incarnation of the Eddystone Lighthouse still signals to ships using its unique pattern of flashing lights and sounds. Each lighthouse has a different pattern of flashes, known as its character, to help sailors distinguish it from other lighthouses as well as a distinct sound pattern produced by its foghorn.

Lamps and lanterns have also been used on ships for many years to send signals and were a particularly important method of communication for ships in convoys during the Second World War. Vessels could send messages to one another even if they were out of sight by bouncing light off low clouds.

Flags
One of the earliest flag systems was developed by a French naval officer, Mahé de La Bourdonnais in 1736. His system consisted of coloured flags representing the numbers 1 to 10 and combinations allowed almost 1,000 different signals to be made. Remarkable advances in technology mean that sailors are no longer isolated from the rest of the world while at sea.

At the end of the 18th century, two British Admirals, Lord Richard Howe and Sir Home Popham developed their own flag codes. Popham’s code became known as Trafalgar Code after it was used in the battle by Admiral Nelson when he sent out the famous message: ‘England that expects every man will do his duty.’

However, it was yet another set of flags developed by the novelist and naval man Captain Frederick Marryat that became most widely used in the 19th century. Marryat’s A Code of Signals for the Merchant Service, published in 1817, was quickly adopted by seafarers and translated into other languages.

Marryat explained the urgent need for an effective system of communication: ‘The Master of a merchant vessel who sees another steering into danger, has at present no means to warn her of it, but must endure the agonising sensation of following her with his eye, till she is dashed to pieces on the rocks; and many a vessel that has sprung a leak, or met with some serious accident, within sight of another, sinks during the night; when had she been able to communicate the particulars of her distress … the crew at least, if not the vessel, might have been saved.’

Subtle signals
Signals listed in Marryat’s code book make interesting reading today, illustrating the many problems facing sailors. Some messages conveyed navigational details such as longitude or that an entrance was narrow.

Others illustrated the problems of health, such as: ‘Has the plague ceased?’ and ‘Was the port you left healthy?’ Some warned of pirates while others dealt with more mundane matters such as: ‘Can you lend us your newspapers?’

Marryat also made provision for signalling at night with a system of four vertical lights coloured red or white to indicate different numbers to correlate with the flag system. Light signals are still used at night.

Marryat’s code remained in use for much of the century but was eventually superseded by The Commercial Code of Signals for the Use of All Nations in 1857. This flag system later became the International Code of Signals and is still in use today and remains the primary method of communication in certain situations.

Radio
In the 1890s, with early radio communications, Morse code began to be used – the rapid succession of short and long pulses represented on paper as dots or dashes.

When Titanic set sail in April 1912, she carried the latest technology of her time. She received ice warnings and, after the fateful collision, her radio officers sent out CQD messages. CQ or sécu is taken from the French word sécurité and, in this context, meant that important safety information was to follow; while D was for distress. So, contrary to popular belief, CQD is not an acronym for Come Quick Danger!

This disaster led to the first meeting of the International Convention for the Safety of Life at Sea (SOLAS) in London on 12 November 1913. See more about SOLAS regulations and IMO on page 6.

The convention ruled that all radios must be permanently manned so as not to miss distress calls, and formalised the use of red flares as a distress signal after Titanic’s flares were not recognised as such by the freighter SS Californian.

Automatic systems
Modern-day radio communication is by VHF radio and these are generally Digital Selective Calling (DSC) enabled. This means that in an emergency a distress call can be made at the press of a button that will carry a boat’s identification number and position.

DSC radios form part of the Global Maritime Distress Safety System known as GMDSS. This international system uses satellite technology and radio systems to ensure rapid automated alerts to shorebased rescue services and other ships in the vicinity.

Mobile phones are notoriously unreliable at sea and satellite phone use has, until now, been limited because of price. However, both the size and price of satellite phones have reduced significantly in recent years. Sailors taking part in round-the-world races post regular blogs with photos and videos and receive messages of support from around the globe.

From 2004 the International Maritime Organization (IMO) required that all ships over 300 tonnes carry automatic identification systems (AIS). This system provides information about the vessel and its destination to other ships and coastal authorities by way of electronic charts pinpointing the position of each boat and its heading.

The RNLI is currently fitting AIS to its entire all-weather fleet and Thames lifeboats. This will enable the Coastguard to track the progress of lifeboats and lifeboat crew to monitor vessels around them.