A drive system, for use with a window covering system including a roller blind mechanism for raising and lowering a window covering fabric, the window covering system also including a continuous cord loop extending below the roller blind mechanism, the drive system comprising: a motor configured to operate under electrical power to rotate an output shaft of the motor; a driven wheel; an electrically powered coupling mechanism including a gear assembly (172, 176, 180) driven by the output shaft of the motor configured to rotate the driven wheel, wherein the driven wheel is able to engage the continuous cord loop to advance the continuous cord loop during rotation of the driven wheel; characterized in that the drive system further comprises a controller for the motor and the electrically powered coupling mechanism, wherein at given times during operation of the drive system, the controller is in one of a machine-control state, a user-control state, and a manual-operation state; wherein the electrically powered coupling mechanism includes an engaged configuration in which rotation of the output shaft of the motor causes rotation of the driven wheel, and a disengaged configuration in which the driven wheel is not rotated by the output shaft of the motor: wherein the electrically powered coupling mechanism is in the engaged configuration when the controller is in the machine-control state or when the controller is in the user-control state; and wherein the electrically powered coupling mechanism is in the disengaged configuration when the controller is in the manual-operation state; wherein the controller for the motor and the electrically powered coupling mechanism monitors a distance of a current position of the window covering fabric from a top position, and wherein in the machine-control state the controller for the motor and the electrically powered coupling mechanism controls an intended displacement from the current position at a given time based upon the monitored distance. a motor configured to operate under electrical power to rotate an output shaft of the motor; a driven wheel; an electrically powered coupling mechanism including a gear assembly (172, 176, 180) driven by the output shaft of the motor configured to rotate the driven wheel, wherein the driven wheel is able to engage the continuous cord loop to advance the continuous cord loop during rotation of the driven wheel; characterized in that the drive system further comprises a controller for the motor and the electrically powered coupling mechanism, wherein at given times during operation of the drive system, the controller is in one of a machine-control state, a user-control state, and a manual-operation state; wherein the electrically powered coupling mechanism includes an engaged configuration in which rotation of the output shaft of the motor causes rotation of the driven wheel, and a disengaged configuration in which the driven wheel is not rotated by the output shaft of the motor: wherein the electrically powered coupling mechanism is in the engaged configuration when the controller is in the machine-control state or when the controller is in the user-control state; and wherein the electrically powered coupling mechanism is in the disengaged configuration when the controller is in the manual-operation state; wherein the controller for the motor and the electrically powered coupling mechanism monitors a distance of a current position of the window covering fabric from a top position, and wherein in the machine-control state the controller for the motor and the electrically powered coupling mechanism controls an intended displacement from the current position at a given time based upon the monitored distance.