–Aelita since episode 27 "New Order".
Tower Control is the ability which Aelita, due to the Annex Program, uses to deactivate said tower that is activated by X.A.N.A. which neutralizes its violent attack in the real world via the special Code: LYOKO.
Since the fifth season, Odd, Yumi, and Ulrich are now capable of deactivating towers as well. This is due to the source codes implanted in their electrolytes by X.A.N.A. himself to ensure his survival.
Since Aelita possessed a fraction of the Keys of Lyoko deep within her subconscious, she has the ability to activate or deactivate Towers at will by entering the Code: LYOKO, neutralizing any X.A.N.A. attack in the real world. Aelita is also capable of entering Code: X.A.N.A. on the interface, which automatically gives control of the Tower to X.A.N.A. when he will most likely delete a sector; he did this with the main four surface sectors of Lyoko.
X.A.N.A., Jeremie and Franz Hopper are also able to activate Towers; a red aura for X.A.N.A., pale green for Jeremie, and white for Franz Hopper. A purple aura appears whenever a tower is activated by Tyron. A neutral tower has a light blue aura.
After William fell under X.A.N.A.'s control, X.A.N.A. used William to do his work on Lyoko and therefore gave William the power to control his monsters and assist in the activation of Towers. Through William, X.A.N.A. is able to gain control of Towers it cannot access alone. William used this once in Double Take. It is shown that William has the ability to give control of Towers to X.A.N.A. by entering the Code: X.A.N.A. in the Tower interface. He had done this on the Forest Replika to break the team's connection to the real world in the episode Lab Rat.
Eventually, Ulrich, Odd and Yumi have recently displayed the ability to deactivate Towers as well, as they had X.A.N.A.'s source codes implanted into their bodies in Code Lyoko Evolution.
As of season 4, Aelita and X.A.N.A.-William are the only ones known to be able to access to the second level of the Tower to deactivate or activate it. This was changed in season 5. The process works the same in both activation and deactivation:
- Enter the tower.
- Walk to the center of the tower.
- Desire to go up to the top
- Walk to the center of the platform
- Put hand on the interface, where one's name appears
- Enter the special "Code" to deactivate said tower or access vital information.
Times when deactivated
- All episodes when X.A.N.A. attacks
- Unlike Aelita, the names of Yumi, Ulrich, or Odd do not show whenever they put their hand on the interface.