Abstract: A method of acoustically obtaining a distance to an object includes transmitting through air an acoustic signal towards an object and receiving a reflected acoustic signal reflected from the object. The time from transmitting the acoustic signal to receiving the reflected acoustic signal is determined. The temperature of the air is determined and used to determined velocity of the acoustic signal. The distance to the object is calculated using the time and the velocity.

Abstract: A display device for the display of information in an environment where the intensity of ambient light varies between high and low levels has a variably intensity light source for illuminating the display and a controller for controlling intensity of the light source automatically in response to a sensed intensity of ambient light energy. The intensity of the light source is controlled between off, low and high values with the light source being off when the intensity of the ambient light is near a high value, low when the intensity of the ambient light is near a low value, and high when the intensity of the ambient light is between the high and low values.

Abstract: A hidden object sensor is described which senses and locates hidden objects hidden behind a surface of an architectural structure. The sensor includes sensing elements for sensing live wires behind the accessible surface, and separate sensing elements for respectively sensing metal and non-metallic objects behind the tested surface. A microprocessor alternates between the use of the various sensing elements and their associated circuits to detect live wires, metal objects, or wood studs. Visible and audible indicators are provided for indicating the device's mode of operation and the locations of sensed hidden objects. If a live wire is sensed, the processor may preclude an indication of a metal object or wood stud.