| 摘要 |
PURPOSE:To enable positive detection of an aircraft located on a ground passage alone, by receiving a reflected pulse from an aircraft and noises thereof with an ultrasonic transmitter/receiver arranged near the passage. CONSTITUTION:First, when an ultrasonic pulse is transmitted from an ultrasonic transmitter/receiver 7, a reflected pulse from an aircraft 5 is received with the transmitter/receiver 7 delayed by a specified time and amplified with an amplification circuit 82 when the aircraft 5 is present within the radiation range thereof. Then, a gate of a receiving gate circuit 83 turns ON in a specified time range to match the driving of the transmitter/receiver 7 with a transmitter 81 and a received signal amplified with the circuit 82 enters a detection circuit 84 to obtain a detection output. An output of the circuit 84 forms a signal containing not only reflected pulse but also noise. Thereafter, the detection output is judged as to the level with a level judging circuit 85 to obtain a detection output P0 containing reflected pulse and noise. When the level of the noise is below a specified value, a pulse detection output is obtained correspondingly to the reflected pulse.
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