Inside was a set of wired drums (rotors and a reflector) that scrambled the input. The machine used a plugboard to swap pairs of letters, and the encipherment varied from one key press to the next.[21] For two operators to communicate, both Enigma machines had to be set up in the same way. The large number of possibilities for setting the rotors and the plugboard combined to form an astronomical number of configurations, and the settings were changed daily,[Note 2] so the machine code had to be "broken" anew each day.[23]