ULTRASONIC THEORY EXPLAINED

Sound pressure waves are transmitted into vehicle by the aptly named transmit head. Frequencies around the 40KHz band ensure the transmissions can not be heard by the human ear.

The sound waves travel through the air within the vehicle cabin and bounce back off all surfaces. Any change in the shape of the surfaces is treated as an intrusion and the sensor triggers the alarm.

Ultrasonic sensors are not suitable for soft-top vehicles and convertibles. Wind blowing through the cabin or wind rustling the soft-top will cause false alarms.

Ultrasonic sensors will not detect movement behind objects blocking the sound waves (i.e. front seats).