A digital modulator for driving a digital amplifier. An air-fuel ratio correction quantity is computed on the basis of the estimated air-fuel ratio of each cylinder and the air-fuel ratio correction quantity is learned by smoothing processing. The ends of the tie are then tied behind the user’s head to secure the tie and endotracheal tube in place between the user’s nose and mouth. A panel band is created from the glued-together standard panels. \u03b8 max: Maximum inclination angle of an inner member.