A method for controlling a door, comprising the steps of storing energy during a manual opening of a door, sensing an object within a doorway, selectively applying a force derived from the stored energy, to close the door, based on the sensing of an object in the doorway. The first contact surface of the first composite panel is disposed above and abuts against the third contact surface of the second composite panel, and the second contact surface of the first composite panel is disposed below and abuts against the fourth contact surface of the second composite panel. By feeding one of four combinations to each of multiple differential output amplifier circuits each having a feedback resistor, the multiple output amplifier circuits can be individually started up or shut down without generating popcorn noise, using only one single time constant circuit. A gutter for relief is cut in the radially inside curved surface in the turnaround in a way extending circumferentially along the turnaround, thereby keeping the separator from coming in any interference with the radially inside curved surface in the turnaround when the separator travels through the turnaround. A tool, such as a rotatable portion of a collar or tool base, or a working instrument operably coupled thereto, is rotatable relative to the interface. There is also described a process for preparing -carmoterol from compound.