Phone keypad
Before touch screens, mobile phones had twelve keys, and to write a message you pressed the same key several times to get each letter. That is called multi-tap. As a cipher, each letter is written as the number of its key, repeated once per press: "HOLA" is "44 666 555 2".
How it works
- Find the key that carries the letter. Key 2 has A, B and C; key 7 has P to S; key 9 has W to Z.
- Write the key's number once per press: A is 2, B is 22 and C is 222.
- Leave a space between letters. Without it, "2 2" (AA) and "22" (B) would be the same.
- Between words, write a 0: on the phone, key 0 typed the space.
- Digits, punctuation and emoji are not encoded: they are left out.
With the 27-letter alphabet, Ñ is on key 6, after N, as on Spanish phones: M is 6, N is 66, Ñ is 666 and O becomes 6666. With 26 letters, Ñ is written as N and O is 666.
A little history
The letters over the digits come from rotary telephones, which already had them to help people remember exchange numbers. When text messages caught on in the nineties, those letters became a keyboard: typing "hola" took nine presses. Then came predictive text, which guessed the word from one press per letter, and later touch screens. Today hardly anyone remembers where each letter was, which makes it a good puzzle.
Try it
Type a message to see its presses, with the keypad drawn beside them. To decode, type or paste the numbers separated by spaces; a 0 or a slash separates words. If a group mixes keys or has more presses than its key has letters, the tool tells you.
No key: the letters are on the same keys on every phone.
- 1
- 2ABC
- 3DEF
- 4GHI
- 5JKL
- 6MNO
- 7PQRS
- 8TUV
- 9WXYZ
- *
- 0space
- #
35 of 600 characters
8 666 6 666 777 777 666 9 0 9 33 0 666 7 33 66 0 8 44 33 0 8 777 33 2 7777 88 777 33 0 222 44 33 7777 8
The key
Each letter, with the presses that type it.
| Letter | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Becomes | 2 | 22 | 222 | 3 | 33 | 333 | 4 | 44 | 444 | 5 | 55 | 555 | 6 | 66 | 666 | 7 | 77 | 777 | 7777 | 8 | 88 | 888 | 9 | 99 | 999 | 9999 |
Classroom ideas
- A message from the past. Present the clue as a text message found on an old phone, with a photo of the keypad as help.
- No key in sight. Older students can work out where each letter is just from knowing that key 2 starts with A.
- A real phone. If you have a number pad or an old phone, let students check the message by typing it.
- From numbers to a lock. Encode a short word and use it as the clue of a text lock: the answer is the word.
Tips
- Write the groups with clear spaces: "4466" cannot be read, "44 66" can.
- With the 27-letter alphabet, point out that O is the fourth press of key 6.
- For younger students, use short words and leave the keypad drawn by hand.
Printable worksheet
Practise this cipher on paper: a worksheet with the key and two exercises, ready to print or download with its answer key. Open the worksheet