Abstract: In order to provide an aircraft navigation computer display unit for use in an aircraft with limited cockpit panel space, the display unit is provided with a housing configured in a rectangular cross-section and includes a cathode ray tube assembly secured in an upper quadrant of the housing, a power supply secured directly below the CRT assembly and a group of circuit boards vertically orientated in the remaining half of the housing in tracks that permit the removal of the circuit boards from the front of the housing. The display unit also includes a front panel assembly having data entry and function switches enclosed therein and an opening aligned with the CRT. The front panel additionally includes a plastic filter secured to a shoulder of the front panel assembly in front of the CRT wherein the filter is located approximately 0.010 inch from the CRT when the front panel is secured to the housing.

Abstract: In order to vary the brightness of the display produced by a cathode ray tube, a digital brightness control circuit is provided that utilizes a source of cathode control voltage connected to the cathode of the cathode ray tube, a brightness selector circuit which is connected to a digital counter, and a resistance network connected to the counter and the cathode control voltage source which is effective to vary in discrete increments the brightness of the cathode ray tube.