Signalling in the Royal Navy

From The Dreadnought Project
Jump to: navigation, search

Signalling in the Royal Navy was a cornerpiece of how command and intent was exerted to and between ships at sea. The complexity, and the media employed in communication had grown and evolved from the Age of Sail.

Signal Flags

The flags that had been used to convey "England Expects..." at Trafalgar would remain the most important tactical medium of command and maneuver signals throughout the Great War era, but signal books would change and, generally, always grow as time passed. Flags were excellent, by virtue of the fairly omnidirectional viewing angle they offered, for communicating command to a fleet of ships, as "Equal Speed Charlie London" demonstrated at the Battle of Jutland, but the mechanism of centralised command they offered delivered a capability that some critics have derided for top-heavy thinking, as Andrew Gordon wrote in his book, The Rules of the Game.


Other forms of visual signalling included Semaphore, which offered fairly reliable but fairly point-to-point communication at 20 (by hand-waved flags) or 15 words per minute (by machine, which presumably boasted longer ranges).[1] Semaphore would seem to offer the greatest bandwidth if you only wanted to address a single other ship.

Other Morse Methods

Morse flag-waving, employing a single large flag swung to through short or long arcs before returning to the rest position, was primarily to be used by landing parties.[2] Also relying on Morse communication were flashed signal lamps (or shutter-equipped searchlights) and heliographs, the latter of which were thought to be useful at up to 10 miles per inch diameter of the mirror, which seems to suggest horizon-reach with quite a compact mirror. Heliographs were also thought to be fairly point-to-point, in that lateral visibility of the reflected beam was 1/107th the range of the viewer, e.g., at 8 miles range, viewers offset 66 yards to either side from the intended target would also see the flashes.[3]

Syrens and whistle blasts could also send Morse code short distances. Within a ship, buzzer circuits based on telegraph keys and sounders and fixed wiring were occasionally used, which seems odd in that Navyphones seem a better choice for such applications.

Wireless Telegraphy

Wireless telegraphy had emerged from the turn of the 20th century to introduce a means of communicating beyond visual range, albeit on a very few frequencies which would be made precious indeed, as only one sender per "tune" would be workable at a time within the transmitting/receiving range of the given instruments.

The Handbook of Signalling, 1918 attempts to spell out the protocols for radio-based telegraphy, but does so with a casual format that does not precisely characterise the method. It does, however, suggest a terribly heavy-handed method that utterly destroys any sense of immediacy one might have hoped the new technology to deliver.

For instance, a short message between two stations might have four to seven times as many taps employed in connection establishment, conveyance of metadata in a preamble and a prefix, and handshaking as were dedicated to expressing who was sending the message, what the message was, and whom was the intended recipient.[4] And yet, despite the overly busy handshaking and acknowledgement suggested in the Handbook, there is little indicate of what happens in cases where the information the recipient was "acking" (often by use of a single dash for "T") was not understood! It seems to cry out for simplification and re-dedication to the fundamentals of what benefits the medium was going to deliver. If this were indeed the method employed during the Great War, a wireless message could not be sent in under two minutes – an estimate that does not even include parts of the process other than the tapping of two attentive and able telegraphers seated at their equipment.

Great War

The Admiralty completed a new Fleet Signal Book in 1913, but plans for its adoption were still underway when war broke out. It was then seen as too risky to adopt the new volume, as it would require speedy widespread promulgation that could easily fail to go smoothly. As a consequence, the existing 1906 edition, with amendments and accompanying Vocabulary Signal Books (of some stripe) were used throughout the war.

See Also


  1. Handbook of Signalling, 1918.. p. 6.
  2. Handbook of Signalling, 1918.. p. 13.
  3. Handbook of Signalling, 1918.. p. 23.
  4. I estimated that if a ship with callsign "AB" wanted to tell station "CD", "HELLO THERE" that this would involve 98 Morse characters being sent (many by the recipient) in a highly interactive and bi-directional conversation in which the flow of transmission would be reversed forty-three times.


  • Fleet Signal Book, 1906 at The National Archives. ADM 186/657.
  • Naval Staff, Signal Division (1918). Handbook of Signalling, 1918. O.U. 5041, 21 November, 1918..
  • Gordon, Andrew (2005). The Rules of the Game: Jutland and British Naval Command. London: John Murray (Publishers). ISBN 0719561310. (on and
  • Kent, Captain Barrie (1993). Signal!: A History of Signalling in the Royal Navy. Hampshire: Hyden House Ltd. ISBN 1 85623 006 6. (on and