The Park Distance Control system is a parking aid that indicates the distance to obstacles behind the vehicle, and in front of the vehicle, thanks to an intermittent warning tone. As the distance decreases, the repeating frequency of the warning tone rises. It first sounds when the vehicle is 1.60 metres from the obstacle. When the driver has just 20 centimetres of manoeuvring space left, a continuous tone sounds. The system uses ultrasonic sensors mounted in the bumpers, which emit and receive pulses in the 40,000 Hz range. When a pulse hits an object, it is reflected. The sensor detects the echo. An electronic analysis system calculates the distance between the obstacle and the vehicle using the time difference between emission of the pulse and detection of its echo. Park Distance Control is automatically switched on when reverse gear is engaged.