Tap code translator
Type text to get the tap pairs, or enter tap pairs such as 2 3 to read them as letters.
About this translator
Tap code is a way of sending messages by knocking on a wall or pipe. Each letter is two groups of taps: the first group counts the row in a five-by-five grid and the second counts the column. The letter K is left out of the grid and replaced by C, so there are 25 letters in five rows of five.
It is best known from prisoners of war, including American prisoners in North Vietnam, who used it to talk through cell walls. The grid is the same Polybius square that ancient Greeks used for signalling with torches.
To tap a letter, knock the row number, pause for a second, then knock the column number. For example H is row 2, column 3, so you knock twice, pause and knock three times. Leave a longer pause between letters. The translator shows the pairs as numbers and as dots, and can play the taps as sound.
The tap code grid
| 1 | 2 | 3 | 4 | 5 | |
|---|---|---|---|---|---|
| 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 |
K is written as C.
Questions
How does tap code work?
Each letter is a row number followed by a column number from a 5 by 5 grid. You tap the row, pause, then tap the column.
Why is there no K?
The grid has 25 cells and the alphabet has 26 letters, so K is written as C. Readers work it out from context.
How do I tap the letter H?
H is in row 2, column 3, so tap twice, pause, tap three times.
Who uses tap code?
It was used by prisoners to talk through walls. It is also taught to scouts, escape-room players and puzzle makers.