tape code

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1 A B C D E
2 F G H I J
3 L M N O P
4 Q R S T U
5 V W X Y Z


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)
W A T E R