1. A motor provides the main force for opening and closing, and controls the acceleration and deceleration of door leaf operation. 2. The tracks that the door leaf moves along constrain the spreader and wheel system to move in a particular direction. 3. The spreader and wheel system is used for hanging door leaves, and drives them run under the dynamic traction. 4. Synchronous belt (some factories use triangle belt) is used to transmit power produced by motor, and then draw the spreader and wheel system. 5. The guiding system is a device set under the door leaf for orientation and positioning, and it can prevent the door leaves from swinging back and forth when in operation.