It is also transmitted to the edges of the displays and controls for general illumination. The overlay has a layer of white paint and a layer of gray paint on the top surface. The panel nomenclature is formed by etching the letters and symbols into the gray paint, leaving the white layer underneath. The panel, mission station and orbit station lighting is controlled by off, var, brt rotary controls on panels O6, O8, R10 and A6. The flight deck instruments have integral lighting that enables the flight crew to read the displayed data.
Lighting is provided by incandescent lamps located behind the face of the instruments.
Prisms are used to distribute the light evenly over the face. Instrument, lighting panel, and orbit station lighting are controlled by off, var, brt rotary controls on panels O6, O8 and A6. The illumination is provided by a single incandescent lamp in each segment of a digit. Seven segments are required to generate the numbers zero through nine. Each numeric indicator has a red light to indicate failures in the indicator and will be illuminated when any lamp in the indicator fails.