The drive motor is switched ON and OFF at variable points within one or both half oscillations of the bell. The electrical energy fed to the drive motor is reduced by shortening the operative duration of the motor per oscillation when the required oscillation of the bell is attained, with the oscillation angle corresponding to the optimal intonation maintained. Pref. the lost energy of the oscillation system per oscillation or half oscillation is determined from the difference between two successive oscillation angles (delta alpha 2), with the energy supplied to the motor controlled to componsate the calculated lost energy.
