ELECTRICALLY OPERATED LINE MONITOR FOR TENNIS

摘要

: An electrically operated line monitor for tennis which used one or more rays substantially smaller in case-section than a tennis ball to monitor areas of a tennis court adjacent to the critical lines. The rays pass over the playing surfaces of the court at a height lower than the height of a tennis ball and when a plurality of rays are employed they are spaced so that a ball in play striking the ground in a monitored area will interrupt the passage of at least one of the rays, thereby actuating a signal. If the rays are monitoring an area just outside a critical line, i.e. an area in which a ball striking in it would be a 'faint', the signal can be an alarm and an additional independant master ray may be provided to monitor the area just inside the critical line and which, if it is interrupted by the passage of a ball, negatives any subsequent signal.