PURPOSE: To satisfy requirements such as for construction and maintenance sufficiently, and to detect whether there is an aircraft with high accuracy, in good consideration of noise protection.
CONSTITUTION: A sensor number set by sensor number setting parts 101, 201 issued from the side of transmission parts 102, 202 of one transmitter/receiver part 10 or 20, is transmitted as a laser beam signal pulse-modulated, for which the sensor number is encoded, while it is judged by the other transmitter/receiver parts 20, 10 whether the sensor number of the signal is a sensor number preliminarily determined by signal process parts 104, 204. When the sensor number is the one issued from a transmitting/receiving means in opposition, it is judged that no aircraft exists, and when it is a different sensor number, it is judged that there is an aircraft. When the judging results differ in both of the transmitter/receiver parts 10, 20, it is judged that the sensor is in abnormal state by this positioning sensor of aircraft.
UEDA KATSUYUKI
SATO TETSUO
MINEO KOJI
TOSHIBA TESCO KK