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The tap code table
The
tap code is a cipher, commonly used by prisoners to communicate with
one another. The method of communicating is usually by "tapping" either
the metal bars or the walls inside the cell, hence its name. It is a
very simple cipher, not meant to avoid interception, since the messages
are sent in cleartext.
Contents
The tap code is
based on a 5×5 grid of letters, representing all the letters of the
Latin alphabet except K (C is used to represent K). Each letter was
communicated by tapping two numbers: the first designated the row
(horizontal) and the second designated the column (vertical). The letter
"X" was used to break up sentences. The tap code requires the listener
to only discriminate the timing of the taps to isolate letters. For
example, to specify the letter "A", one would tap once, pause, and then
tap once again.
Or to communicate the word "WATER" the cipher
would be the following (the time between each pair of numbers is smaller
than the one between two different letters):
..... .. . . .... .... . ..... .... ..
(5,2) (1,1) (4,4) (1,5) (4,2)
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