| 摘要 |
Liquid crystal display units are finding increasing application in electrical appliances used for communications. If the appliance is for example a handset for a mobile radio transceiver and is held in a cradle on the dashboard, the angle of observation will change depending on whether the receiver is placed in the cradle or held in the hand. To ensure that the recognizability of the displayed information is not impaired upon a change in the position of the receiver, a control circuit automatically changes the contrast when such a change takes place. The circuitry required for this control is particularly simple when two different voltage values are generated by means of a switchable voltage-divider for two preset positions of the appliance. The switching takes place between the two voltage values in dependence upon the position of the cradle hook switch. The contrast (i.e. the amplitude of the voltage) is increased to a level which ensures that the displayed information is clearly legible from the new angle of observation.
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