| 摘要 |
A ball, for use in ball game indicating systems which comprise spaced electric ground leads as part of a circuit intended to be closed by an impacting ball having conductive adhesive, seams, and surface elements, such ball having requisite electric conductivity and high visibility in flight, wherein a. at least 75% of the playing surface of the ball is light colored, and b. a plurality of separate elements forming spaced electric leads have been provided on not more than 25% of the playing surface of the ball, said electric leads i. comprising a dark-colored, finely divided electrically conductive substance, ii. having defined shape and a width of at least 2 millimeters, iii. being spaced so that on the playing surface of the ball no lead is separated from the next nearest lead by more than 20 millimeters, and iv. having overall dimensions so that leads on the playing surface of the ball touching the ground connect two ground leads at the moment of impact of the ball.
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