| 摘要 |
The method monitors parking spaces in a car park by an ultrasonic signal to determine whether they are vacant or full. The ultrasonic signal is emitted periodically for a predetermined duration to form a train of ultrasonic pulses. The time between the emission of the signal (7) and the reception of the reflected signal (8) is measured by a receiver (4) adjacent to the emitter (3). The distance travelled by the ultrasonic pulse can then be determined. If this distance is less than a reference distance the parking space is occupied.
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