| 摘要 |
Apparatus for providing illuminated columns or signals for use as first down lines of demarcation on football fields. The signs may comprise: (1) a single laser light beam having a luminous horizontal segment directed across the field and serving as an overhead line of demarcation, in combination with a relatively lower parallel luminous segment of the same beam, reflected reversely across the field and serving as a ground line of demarcation, or (2) two oppositely travelling light beams having a pair horizontal luminous segments serving as a composite overhead line of demarcation, in combination with a second pair of horizontal relatively lower luminous segments of the same beams serving as the ground line of demarcation, or (3) either the overhead or the ground line of demarcation of the last-named combination. During a game, the sign is used as a reference by game officials, players, and spectators for approximating and/or determining the relative position of a football lying on the field at the beginning of or between successive downs.
|
