Semaphore Angle

A semaphore angle is a graphic representation of the classic two-arm semaphore used in maritime signaling.

In the classic system, two arms holding flags are oriented along discrete angular directions. In a semaphore angle, these arms are replaced by two segments forming an angle.

Each letter is associated with a configuration formed by two segments oriented in eight possible directions.

The standard semaphore correspondence table allows each configuration to be associated with a given letter:

A		B		C		D		E		F		G
H		I		J		K		L		M		N
O		P		Q		R		S		T		U
V		W		X		Y		Z
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Decoding a semaphore angle involves identifying the two directions of the segments relative to the vertical.

The user notes the two orientations and then consults the standard semaphore table to convert this pair of directions into the corresponding letter.

A semaphore angle is identified by its two segments oriented in directions that are multiples of 45°.

The segments can form a zero angle (overlapping segments), an acute or obtuse angle, or a straight angle of 180°.

Several systems use coded visual configurations:

— Maritime semaphore: two flags held at arm's length form angular positions corresponding to the letters of the alphabet.

— Clock semaphore: the arms are replaced by two hands positioned as on a clock face.

— Chappe optical telegraph: a system of articulated arms installed on towers, allowing long-distance visual communication thanks to a code based on the position of the elements.

— Visual Morse code: light signals corresponding to temporal sequences of dots and dashes, based on duration rather than angular position.