A method for electrically controlling at least one functional element having electrically controllable optical properties, wherein the optical properties are controlled by a control unit, wherein the control unit is connected to at least two transparent flat electrodes of the functional element, and an electrical voltage is applied between the flat electrodes by the control unit, wherein the electrical voltage has a periodic signal profile with a first, variably adjustable frequency and the glazing unit is surrounded by light beams of a second frequency, and wherein the light beams are sensed by a sensor unit and the first frequency is changed as a function of the second frequency, wherein the first frequency is synchronized with the second frequency.