Semaphore is a visual method of communication that involves signalling the alphabet or numbers by the hand-holding of two flags in specific positions. It has been described as ‘Optical telegraph‘.
The flags are coloured differently, depending on whether the signal is sent over the land or across the sea.
Red and yellow flags (the Oscar flags) are used at sea and are similar to some beach surf signs see in the U.K. and around the world.
The system was developed in France in 1790 by Claude Chappe and his brothers. This was the time of the French Revolution and there was a great need for the government to be able to quickly communicate orders and to receive information.
Their first message, on March 2, 1791 was sent a distance of 10 miles and read:
“If you succeed, you will soon bask in glory.”
(‘Si vous réussissez, vous serez bientôt couvert de gloire.”)
They used black and white flags initially, as well as clocks, codebooks and telescopes.
Over the next few years, the Chappe bothers set up a network of 556 stations around France and towers, with large, moveable wooden arms were developed. The system was expensive to operate, requiring people to ‘man’ each station continuously during the hours of daylight. The staff had to be very skilled and attentive in order for the system to work. Once the success of the system was realised, many other countries adopted the semaphore system, including Sweden, England and Germany.
The system of handheld flags was further developed during the early 1800’s when the maritime industry found that the flags were a fast and easy method to communicate between ships.
It is still an accepted form of communication during an emergency, using flags in the daytime and torches at night.