Abstract: When a light emission element emits no light, a detected signal from a photodetection element is captured as an intensity of external light. Then, a threshold value is offset by the intensity of the external light. The offset threshold is then compared to a detected signal from the photodetection element when the light emission element emits light, thereby determining the presence of a through hole between the light emission element and the photodetection element through which hole light passes without being influenced by external light.

Abstract: When a light emission element emits no light, a detected signal from a photodetection element is captured as an intensity of external light. Then, a threshold value is offset by the intensity of the external light. The offset threshold is then compared to a detected signal from the photodetection element when the light emission element emits light, thereby determining the presence of a through hole between the light emission element and the photodetection element through which hole light passes without being influenced by external light.

Abstract: A position determining system, a receiving system, a method of determining the position of a movable object and a method of receiving data regarding the position of the movable object are provided. The position determining system comprise a position determining unit, a display unit and a controller. The position determining unit determines the position of a movable object based on position information sent from GPS satellites. The display unit displays the position of the movable object which has been determined by the position determining unit. The controller controls a time interval at which the position of the movable object is determined by said position determining unit, in accordance with a degree of position change occurring in the position to be displayed on the display unit. Accordingly, in the position determining system, elimination of consumption power can be realized in a position determination process which is not necessarily performed, while the system is advantageously handled.