System for monitoring the marking lines in ball games

摘要

The invention makes it possible to determine whether the ball has struck the marking line of the playing area, displaying this acoustically and optically, even in the event that the player's foot was already on the marking line or that the latter has simultaneously made contact with the ball. To this end, the invention uses as the marking line a rubber hose of rectangular cross-section which is connected to a piezoelectric pressure converter. The pressure changes which arise as a result of the impact of the ball or foot on the rubber hose are electronically analysed, the principal fact evaluated being that the pressure changes which the foot produces are at least ten times slower than those which the impact of the ball on the marking line generates.