| 摘要 |
<p>The vertical face of the box is a fixed or removable opaque sheet in which square windows are arranged in equidistant horizontal and vertical lines. The letters, pref. capitals, are formed by partial blackening of transparent rectangular tiles which slide along horizontal grooves fromed in the face above and below each row of windows. When a whole row of tiles is inserted from one end with the leading tile arrested by a stop at the other end, one letter appears centrally in each window and is illuminated from within by a single filament lamp. Interword spaces are constituted by completely blackened tiles in appropriate positions. The sign is easily transportable and legible in daylight at several metres' distance.</p> |
