An infrared touch screen surrounds the face of the display with a bezel of light-emitting diodes
(LEDs) and diametrically opposing phototransistor detectors. A sequence of pulses is directed
to each of these LEDs by the controller circuitry directs, which scan the screen with invisible
infrared light beams just in front of the surface. The controller then detects the location where the
light beams become obstructed by any object.