The Houdini Code is a code used by the American escapologist and magician Harry Houdini to communicate with his assistant.

The numbers 1 to 10 or the letters A – I were coded with words.

Pray = 1orA
Answer = 2 or B
Say = 3 orC
Now = 4 orD
Tell = 5 orE
Please = 6 orF
Speak = 7 orG
Quickly = 8 orH
Look = 9 orI
Be Quick = 0 or 10 or J

Entered letters or numbers are encoded according to the table above.

Entered words are decoded according to the table above.

BE QUICK is interpreted as o or 10 in each case.