Abstract: A long or triple jump foul detector system is disclosed which very accurately detects a foul by an athlete when a portion of an athlete's shoe crosses over a foul line when beginning the jump. A laser beam is emitted parallel to and directly above the foul line. A laser beam detector detects interruption of the laser beam by the athlete's shoe and a foul detector provides a foul indication. An audible foul indication is delayed so as not to interfere with the athlete's jump. Also, the system may provide additional detection of an athlete's foot crossing a training line positioned in front of the foul line. Furthermore, the system distinguishes between a relatively quick interruption of the beam caused by the athlete's shoe when jumping, and a relatively slow interruption of the beam which may result such as by a judge placing his or her hand in the beam when measuring a jump.