To encipher a message, the inner disk was turned until the desired letter was at the top position, with the number of turns required for the result transmitted as ciphertext.
Stream ciphers typically encrypt plaintext a bit or byte at a time, and are most commonly used to encipher real-time communications, such as audio and video information.
Like many machines of the era it used an electromechanical system of rotors in order to encipher messages, but with a number of security improvements over previous designs.