Phototube Detects Bowling Fouls (Jan, 1933)
Phototube Detects Bowling Fouls
A PHOTO-ELECTRIC tube now makes it impossible for bowlers to step on or over the foul line without being detected. A small beam of light is focused across the alley so close to the floor as to be intercepted by nothing except the player’s toe, which needs to slide across the foul line but a fraction of an inch to be detected and registered by a flashing red light.
The light source is a small incandescent lamp which is focused by a lens into a narrow beam across the alley to the photoelectric cell. The instant anything intercepts this beam, cutting down the amount of light which hits the electric eye, the tube actuates a relay turning on the red light which indicates a foul.