Abstract: A lifting device is provided. The lifting device includes a stationary member, a lifting member, positioning bases, reels, and springs. The lifting member is slidably coupled to the stationary member. The lifting member is fixed to a back portion of the display. The positioning bases are disposed on the stationary member and the lifting member. The reels are pivoted on the positioning bases. The springs are wound around the reels and connected to the other of the stationary member and the lifting member relative to the positioning bases. When the display or the lifting member is subjected to an applied force toward a sliding direction, the lifting member slides toward the sliding direction relative to the stationary member. The springs stretched by the lifting member generate an elastic force, so that the lifting member and the display no longer subjected to a force stay at a height position after sliding.

Abstract: An ultrasonic-based person detection method. The method comprising the steps of: (a) emitting, from an emitter, an ultrasonic signal, the ultrasonic signal including a component at a first frequency; (b) receiving reflections of the ultrasonic signal, the received signal including components at frequencies greater than and less than the first frequency; (c) determining a difference between an upper portion of the received signal containing a frequency higher than the first frequency, and a lower portion of the received signal containing a frequency lower than the first frequency; and (d) determining, based on the difference between the upper portion and the lower portion, whether a person is present.