Abstract: A gas flow indicator including an open-ended cylinder, a piston constrained within the cylinder to move between the ends thereof, and a reed switch positioned on the outside of the cylinder for responding to the position of a magnet secured to the piston is disclosed. The piston is closed at its end adjacent the output aperture of the cylinder and is open at its end adjacent the input aperture of the cylinder for defining a basin within the piston. A spring is positioned between the piston and the output aperture for forcing the piston away from the output aperture. Gas flowing in through the input aperture forces the piston toward the output aperture. An indication of the state of gas flow through the cylinder is provided in accordance with whether the switch is open or closed.

Abstract: A display device for use with a photographic system that includes a platform for receiving objects to be photographed and a support for a camera used for photographing objects received on the platform. The display device includes a plurality of digit sections arrayed to provide a display of a multiple digit number, a keyboard device for selecting characters to be displayed and an electrical circuit. Each of the digit sections includes a display element having an array of a plurality of segments that are separately actuated in response to predetermined combinations of electrical signals for providing a display of a selected numeric character. The electrical circuit provides the predetermined combinations of electrical signals in response to the operation of the keyboard, and further includes counters for increasing the displayed number by one count in response to a predetermined input signal.