Tap Code Tool

What is Tap Code?

The tap code is a simple way to encode messages. The messages are sent by translating letters into knock sounds. It was used by prisoners in Vietnam, and is sometimes called knock code or Smitty code. It uses a 5x5 square to assign two numbers (row and column) to each letter. Then the sender knocks as many times as each number, and makes pauses between the numbers.

Tap Code Tool

Message:

Tap Code:

Code Type:

Example

Let's look at the word HELLO. First translate it to numbers using the square (a so-called Polybius square):

            H  E  L  L  O
            23 15 31 31 34

The Tap Code Table

Then translate them to dots:

            2  3    1 5      3   1  3   1  3   4
            .. ...  . .....  ... .  ... .  ... ....

Features

Tap code has similarities with Morse code, but only short "beeps" are used.
Like Morse code, tap code can be transmitted in various ways and in difficult environments.
Other names for tap code include knock code and Smitty code.
A Russian variant exists, using a 5x6 rectangle of Cyrillic letters instead of the 5x5 square.
A variant of tap code was featured in Kurt Vonnegut's novel Player Piano.

Tap Code / Knock Code

What is Tap Code?

Tap Code Tool

Tap Code:

Example

The Tap Code Table

Features

See Also