a system for capturing the position of a moving object , using a marker that is a passive component , and a sensor that is an active component . the sensor is carried or attached to the moving object and the marker placed at a stationary location . when the distance between the sensor and the marker is less than the detection range of the sensor , the sensor automatically detects the presence of the marker and produces a detection signal . the sensor has an electronic circuit of the sensor with a clock device and a storage unit , so that the time the signal is generated is automatically stored .