Importance

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Abstract

A liquid-crystal display preferably eighteen lines of forty characters each, is mounted in a case. The temperature of the display medium is held within operating limits for the display--notwithstanding ambient temperature and humidity variations over generally normal ranges for at least the temperate zones, and even if the display unit receives direct sunlight. The unit works outdoors, at temperatures to at least 46.degree. C. (115.degree. F.) as well as in buildings with no temperature control. This is accomplished by use of a shading hood, and a window (preferably unperforated polycarbonate, curved, upward-and-outward-concave, and cylindrical-segment) that reflects to a viewer only light from the hood underside. No ventilating fan, plenum or other ventilating opening is needed. A circuit-board-mounted temperature sensor controls the contrast-adjusting voltage of the display--using data in a digital-memory 'look up' table. A heater is preferably provided, also temperature-controlled. The entire unit can be flush-mounted in a wall without disrupting operation. Visible glare arising in reflection at the window is reduced by the hood-and-window combination, without need for any antireflection coating on the window.

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First Claim