LIQUID-CRYSTAL DISPLAY UNIT FOR ELECTRONIC DIRECTORY

摘要

A liquid-crystal display, preferably twenty-five lines of eighty characters each, is mounted in a case. The temperature of the display medium is maintained 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 is placed to receive direct sunlight. The unit works outdoors as well as in buildings that lack temperature control. This is accomplished preferably by circulating air from outside the case through a space between the display face and an unperforated protective polycarbonate window. Intake and exhaust plena are long and narrow enough to deter manual access to the display and thus van dalism; however, the plena are straight and sufficiently free of obstructions that the fan can be a very small, low-power, quiet unit. A temperature sensor controls the fan, and also the contrast-adjusting voltage of the display -- based on data in a digital-memory "look up" table. A heater is preferably provided, also temperature-controlled. The plena face downward so that the unit is not sensitive to rain, and the entire unit can be flush-mounted in a wall without disrupting system cooling. Visible glare arising in reflection at the window is reduced by an antireflection coating on the window.