A method of controlling the drive of conveyor installation which includes a drive motor (26) and a frequency converter (42) whose output is adjustable, between a load operation and an idle mode, in the form of an escalator (10) or a moving sidewalk, where: in the load operation mode drive motor (26) is supplied with a line voltage at an essentially constant line frequency (fNetz), and in the idle mode with an output voltage of the frequency converter (42); the line voltage and the frequency converter's output voltage are compared with respect to frequency and phase position; the frequency converter (42) is set for an output frequency which has a predetermined spacing (&Dgr;fup, &Dgr;fdown) from the line frequency (fNetz); a demand to switch modes is signalled by a conveyance signal generator (48); and at the point in time (t1, t4), after a demand to switch modes has been signalled, when the output frequency of the converter (42) has reached the predetermined frequency spacing (&Dgr;fup, &Dgr;fdown) from the line frequency (fNetz), and a predetermined phase spacing has been achieved between the frequency converter's output voltage and the line frequency (fNetz), a switch-over signal (58) is emitted to switch the drive motor (26) between the frequency converter supply and the line supply.