Abstract: An airway obstruction luminaire has a luminaire base; a substantially cylindrical Fresnel lens having a lens axis; a halogen lamp having a lamp base, and a substantially linear filament; and a lamp bracket which positions the lamp such that a filament axis of the filament is coincident with the lens axis. The filament is energized by a power supply connected to a first filament end and second filament end, which are separated by an effective length l.sub.E of less than 1 inch. The filament is preferably formed as a helical coil. The lamp is designed to operate at a lamp rated voltage V.sub.L between about 12 and 30 volts. The power supply voltage V.sub.P is reduced if V.sub.P is greater than V.sub.L. The second filament end is supported by a second end support structure configured to reduce shadowing. The lens is preferably an acrylic plastic lens fabricated by injection molding.

Abstract: A direction finding system is disclosed in which a predetermined horizontal plane is established by the projection from one location of an image having illuminated and unilluminated portions corresponding to the predetermined horizontal plane. A receiver at a remote location detects the image at two spaced points and produces an indication of the center of the transition zone between the illuminated and unilluminated portions of the projected image.

Abstract: A direction finding system is disclosed in which a predetermined horizontal plane is established by the projection from one location of an image having illuminated and unilluminated portions corresponding to the predetermined horizontal plane. A receiver at a remote location detects the image at two spaced points amd produces an indication of the center of the transition zone between the illuminated and unilluminated portions of the projected image.