The idea of sending messages using signal flags has been around for centuries. Visual communication was valuable as the use of voice or other audio communications was often unreliable. Some uses of flags as signals are noted as early as the 1500s. Systems of flags representing numbers were developed by multiple European nations up to the 1800s. But there was no standardization of signal flags and their codes for nations to rely on.
The first standardized system was introduced in 1857 by Britain. Flags were chosen to represent numbers and consonants from the alphabet. This system was revised in 1901 to include all letters of the alphabet, and was revised again in 1931 and 1969.
The modern system uses 3 shapes of flags with up to 5 bold colours arranged in different patterns. Flags that represent letters of the alphabet can be used to spell out messages. They have their own meaning. For example the signal flag L means “stop your vessel immediately,” but when it’s combined with the O flag, the message becomes “stop your vessel immediately. Man overboard.”
By using letters, single or in a combination, communication between boats can be short, effective, and quick.
The signal flags below showcases the respective phonetic names and International Code of Signals (ICS) meanings as single flags.
These images from a homemade set of flash cards that were used to learn and to test the International Code of Signals.
VMM item number 2019.999.424.
Sebastian Francisco de Bigot created the first established system for coded flags (336 signals.)
Admiral Lord Howe used a numeral flag system and signal book.
The number flag system was created by Captain Frederick Marryat and was first widely used in the early 1800s.
New system using flags representing letters and numbers (some 40,000 codes created) called the Commercial Code (18 signal flags at the time used to create 70,000 messages.)
New international standards established in 1901 introduced vowels.
Revised in 1931 to be more effective and efficient; no longer signaling words.
Photo Credit: Vancouver Maritime Museum
VMM item number HCSR-40-13.
Bill (William Michael) Cashin who had the position of a Special Constable stands aboard the St. Roch. A banner of North West Passage logo and a few flags are shown in the background.
VMM item number HSUS-50-07.
The St. Roch returning from travelling through the Panama Canal with its signal flags placed on the dressing lines as a sign of celebration.
VMM item number HCSR-100-11.
Henry Larsen aboard the St. Roch with signal flags on the dressing lines surrounding him. Signal flags are displayed in this manner for special occasions and celebrations.
VMM item number LM2019.999.020.
This signal card for Gibraltar Garrison (Britain Force) consists of drawings of signal flags and the definition of each flag.
VMM item number VK 381 G7 1913.
A diagram from the the Handbook of Signalling 1913, showing the proper form for an individual displaying a signal flag.