Flag Semaphore

The Semaphore encryption uses 2 flags (or other visual element, usually red and yellow) and a person, if possible standing (so as not to hinder arm movements).

Each letter as well as the character space is represented by a flag, the digits (1234567890) are represented by the letters from A to K.

Example: DCODE is translated

There are 3 special flags:

Which allows to pass from the digits to the letters

Which allows to pass from letters to numbers

Which indicates an error or danger

Example: A1 is translated

Usually, the flags are presented in the reception mode, the transmitter looks towards the receiver (a person emitting a message will have to imagine the character mirrored).

Semaphores signals decryption is done by matching the positions of the flags with the letters of the alphabet.

Example: translates to SEMAPHORE

The message consists of humanoids with flags (or any other object) presented at the end of a stretched arm with multiple angles of 45 degrees (0, 45, 90, 135, 180, 225, 270, 315, 360).

Any reference to the aviations, planes, or boats, the places where these flags are used is a clue.

Clock hands (set to hours, half hours or quarter hours) are a way of hiding semaphores.

Sometimes the flags are used to code Morse, with 2 defined positions corresponding to point and dash.

Maritime signal codes uses another principle of flags to encode words.

The system of flags and the alphabet spread throughout the world in the 19th century.