Abstract: A drive suitable for a door or gate operator mechanism has a motor (1) and a gear box (5). The gear box (5) has a drive disengaging means (29) therein which can be pulled by a chord (7) to effect drive engagement of the motor (1) with the gear box (5). When the chord (7) is next pulled drive disengagement of the motor (1) with the gear box (5) is provided. The arrangement permits a door or gate which is driven by the operator to be manually opened in the event of power failure. The mechanical advantage of the gearbox (5) and the motor (1) on the door or gate is such that the gate cannot be manually opened without the drive being disengaged.