Semaphores – the marine signal language

The word Semaphore derives from the Greek words sema (sign) and foros (bearer).  Semaphore Flags is the system for conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the flag is in a fixed position. Semaphores were adopted and widely used (with hand-held flags replacing the mechanical arms of shutter semaphores) in the maritime world in the 19th century.  It is still used during underway replenishment at sea and is acceptable for emergency communication in daylight or, using lighted wands instead of flags, at night.

Optical “telegraphs” or signaling devices have been traced back to ancient times (using torches) and were the fastest systems to convey messages over long distances. These “telegraphs” could have since been in the form of torches, smoke signals and eventually semaphore towers.

Semaphore towers used large blades/paddles to convey messages. These messages were decoded based on the fixed positions of these arms and could transmit signals up to 150 miles in two minutes using multiple towers.  In France, this was the primary source of communication for military and national applications, until it became more widely used in the 1850′s. Designs varied between using shudders open and closed to holes being open and closed.  Even Napoleon used one design to communicate to his army strategies and locations of his enemies. These semaphore stations were so successful that the French government rejected Samual Morse‘s first proposals of the electrical telegraph, citing that its design was flawed by wires being able to be cut easily.

These visual messaging systems eventually led to semaphore flags. These flags were used in the same way that the arms were used on the semaphore towers – different fixed positions mean different messages. Semaphore flags were primarily used for naval applications to communicate message between boats. It proved to be a very useful tactic during battles, most famously the Battle of Trafalgar during the Napoleonic Wars.

The flags are usually square, red and yellow, divided diagonally with the red portion in the upper hoist.

The flags are held, arms extended, in various positions representing each of the letters of the alphabet. The pattern resembles a clock face divided into eight positions: up, down, out, high, low, for each of the left and right hands (LH and RH) six letters require the hand to be brought across the body so that both flags are on the same side.

One way to visualize the semaphore alphabet is in terms of circles:

  • first circle: A, B, C, D, E, F, G;
  • second circle: H, I, K, L, M, N (omitting J);
  • third circle: O, P, Q, R, S;
  • fourth circle: T, U, Y and ‘annul’;
  • fifth circle: ‘numeric’, J (or ‘alphabetic’), V;
  • sixth circle: W, X;
  • seventh circle: Z

In their first circle, the letters A to C are made with the right arm, and E to G with the left, and D with either as convenient. In the second circle, the right arm is kept still at the letter A position and the left arm makes the movements; similarly in the remaining circles, the right arm remains fixed while the left arm moves. The arms are kept straight when changing from one position to another.

Today these flags have become smaller and are usually mounted to small dowels or poles to allow them to be seen easier. Maritime use flags are red and yellow (or the OSCAR) flag and while in land use, the flags are blue and white (or the PAPA) flag. Even though they are not in use much anymore, they still serve for some boats and ships.

So why did we get rid of them?

There were two critical downfalls of all the systems:

  1. They had no secrecy. Everyone within visual distances could see the message and therefore react to it. This proved to be one of the design’s most fatal wartime attributes.
  2. They were practically invisible at night time and during heavy fog and rain.

Both of these reasons lead to the electrical telegraph and Morse Code, both “invented” by Samuel F.B. Morse.  From there we went to electrical telegraphs, pony express, telephone, radio, television, computers, fax machines, satellite televisions, cellular phones and the internet. Ultimately semaphore flags and towers inspired all designs since.

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