A method of controlling the drive of a conveyor installation in the form of an escalator or a moving sidewalk between a load and an idle mode, the conveyor installation comprising a drive motor, a conveyance signal generator, a synchronizer and a frequency converter whose output is controllable, where: in the load operation mode the drive motor is supplied with a line voltage at an essentially constant line frequency (fNetz) and in the idle mode with an output voltage from the frequency converter; the line voltage and the frequency converter's output voltage are compared with respect to frequency and phase position by the synchronizer; the drive motor operates without current during a predetermined zero current time (Δti) before the switch-over between line supply and frequency converter supply takes place; the frequency converter is adjusted for an output frequency which has a predetermined spacing (Δfup, Δfdown) with respect to the line frequency (fNetz) which corresponds to the decrease in RPM of the drive motor during the respective zero current time (Δti); a demand to switch over the mode is signalled by the conveyance signal generator; and at the point in time (t1, t4) after a demand to switch modes has been signalled, when the output frequency of the converter has reached both the predetermined frequency spacing (Δfup, Δfdown) from the line frequency (fNetz) and a predetermined phase spacing between the frequency converter's output voltage and the line frequency (fNetz), a switchover signal is emitted by the synchronizer which switches the drive motor between the frequency converter supply and the line supply, wherein the switch-over takes place by means of a switch-over installation (K1, K2) with an inherent switch-off delay (Δtd) with respect to time (t1, t4) when the switch-over signal is received, wherein a switch-over between the frequency converter supply and the line supply is ordered with a lead time which corresponds to the sum of the switch-off delay (Δtd) and the zero current time (Δti), with respect to the time (t3, t6) when a switch-over between frequency converter supply and line supply shall take place, wherein a value which corresponds to the phase change in the motor terminal voltage during the lead time is used as the predetermined phase spacing, so that at the end of the lead time an essential match is obtained between the phase positions of the motor terminal voltage and the frequency converter's output voltage. in the load operation mode the drive motor is supplied with a line voltage at an essentially constant line frequency (fNetz) and in the idle mode with an output voltage from the frequency converter; the line voltage and the frequency converter's output voltage are compared with respect to frequency and phase position by the synchronizer; the drive motor operates without current during a predetermined zero current time (Δti) before the switch-over between line supply and frequency converter supply takes place; the frequency converter is adjusted for an output frequency which has a predetermined spacing (Δfup, Δfdown) with respect to the line frequency (fNetz) which corresponds to the decrease in RPM of the drive motor during the respective zero current time (Δti); a demand to switch over the mode is signalled by the conveyance signal generator; and at the point in time (t1, t4) after a demand to switch modes has been signalled, when the output frequency of the converter has reached both the predetermined frequency spacing (Δfup, Δfdown) from the line frequency (fNetz) and a predetermined phase spacing between the frequency converter's output voltage and the line frequency (fNetz), a switchover signal is emitted by the synchronizer which switches the drive motor between the frequency converter supply and the line supply, wherein the switch-over takes place by means of a switch-over installation (K1, K2) with an inherent switch-off delay (Δtd) with respect to time (t1, t4) when the switch-over signal is received, wherein a switch-over between the frequency converter supply and the line supply is ordered with a lead time which corresponds to the sum of the switch-off delay (Δtd) and the zero current time (Δti), with respect to the time (t3, t6) when a switch-over between frequency converter supply and line supply shall take place,