Naval Communications down the ages
Early signalling at sea was by means of the signal cannon. The invention of the telescope in the 17th century led to the development of optical signalling systems, the earliest using flags. Instructions for the Better Ordering of the Fleet in Fighting, by Admiral Robert Blake in 1653 gave a limited range of messages which could be sent, depending on which of five flags was flying at certain positions on the masts.
In 1782 Admiral Lord Howe had a system based around ten flags representing the numerals, and this was used in conjunction with a printed code book. In different combinations, used either as whole words or single letters, the flags could form any sentence. The dictionary contained 260 words represented by number combinations. This was developed further in 1803 by Admiral Sir Home Popham, in Telegraphic Signals of Marine Vocabulary and expanded so that there were 3000 words in the dictionary.
The Popham code was the one used by Nelson at Trafalgar. He wanted to start the signal "England confides..." but his signal officer, Lieutenant Pasco, suggested a change since "expects" was in the dictionary but "confides" was not. The signal locker on HMS Victory was at the back of the poop deck, and the signals were made using the mizzen mast only. The signal was preceded by the Telegraph flag, then there was a series of twelve hoists to send the full signal. Each hoist was kept flying until all the ships addressed had hoisted the acknowledgment meaning that they had seen and understood the signal.
With a large fleet like Nelson's at Trafalgar, this could take a long time and to facilitate signalling in such circumstances, frigates were stationed along the line to windward to repeat the signal for the benefit of the ships furthest away. The acknowledgements were in turn repeated by the frigates for the flagship's benefit. For all of Nelson's ships to have read and understood such a long signal in the space of only four minutes reflects great credit on the competence of the signal officers and signalmen in the fleet.
While signal flag systems were developed at sea, the Royal Navy developed different systems for signalling from the Admiralty to their Naval bases. The system of semaphore devised by Lord George Murray utilised six shutters, two vertical rows of three - on a white background. These shutters could be changed from white to black thus making a distinctive pattern to represent the letters of the alphabet. Relay stations were set up on towers from London to Portsmouth, and London to Deal. Each station would read the message through a telescope and relay it to the next station. In this way a message could be sent the Admiralty in London to the fleet at Portsmouth in about twenty minutes. This system was naturally of no use during the night or in foggy weather.
After the Napoleonic wars were over, the Admiralty adopted the French semaphore system invented by Claude Chappe in 1791, which used two mechanical arms to represent a total of 49 different positions.
Land-based semaphore gave way in the nineteenth century to the electric telegraph, with a Cooke & Wheatstone system provided signalling from London to Gosport in 1844.
Naval signalling was much improved with the coming of wireless, and the Royal Navy used Marconi wireless equipment in 1899 during the Boer War. Ships could now communicate with each other at sea and also with shore stations. All communication was by use of Morse code.
By 1904 the Royal Navy had adopted transmitters fitted with alternators and used magnetic detectors with headphones, replacing the much less sensitive coherer and inker. The sinking of the Titanic in 1912 focussed public attention on the importance of ships being equipped with radio and the necessity for maintaining 24 hour radio watch.
With the invention of the Thermionic Valve, radio communication was again improved and the Royal Navy saw the need to train large numbers of operators. Communications training schools were set up and sailors were taught Morse code and Naval signalling procedure. The radio side of this became separated from flag signalling. In Naval parlance a signalman was either a "Sparker" or a "Bunting Tosser".
Morse code continued to play a major role in Naval communications throughout World War II. Morse can easily be encrypted before the message is sent and messages were often sent as letters or numbers in groups of five. Using a flashing light to send a signal from one ship to another in a convoy was important as radio silence could be maintained.
As time moved on great advances were made with signalling. The modern warship uses satellite communications and has an extensive Local Area Network on board. Nevertheless the humble "Sparker" still needs to use visual signalling by Morse and flag for close range secure communications. Recruits start at HMS Raleigh in Cornwall and then progress to the Royal Navy’s signals centre at HMS Collingwood in Hampshire, named after Admiral Cuthbert Collingwood who was Nelson’s second in command at Trafalgar.