| 摘要 |
<p>The road traffic guiding device incorporates a movable transparent element as a dirt interceptor in front of its reflector or light aperture; a section of this element is removed from the effective visual area and replaced by an adjacent section; an electric, spring tension, or other power source is connected to the element and operated at fixed time intervals by a control device. This control device is in the form of a time switch mechanism, charged with one or more switching programmes. The programmes are automatically selected, delayed, varied, annulled or completed, by factors including air temperature, air humidity, the degree of dirt on the dirt interceptor, or any desired combination of these. This is inexpensive, and reduces the use of power, so that devices which can only be checked at long intervals can be relied on to keep the road signs operating visibly.</p> |
