Abstract: Apparatus for detecting and computing the location of a baseball as it is pitched over a plate is disclosed. Infrared receivers are disposed at corner locations on opposite sides of a target zone which is aligned with the plate. First and second arrays of infrared emitters are mounted on opposite sides of the target zone for transmitting infrared light pulses to the opposite corner receivers. The infrared emitters are sequentially energized and transmit infrared pulse signals having relatively short durations in a scan cycle. Digital data words representative of the reception and nonreception by the receivers of the optical pulse signals are generated during each pulse interval of the scan cycle. Computer circuitry calculates the coordinates of the baseball within the target zone as a function of predetermined angular data retrieved computer memory.