The sensor system that is used most often is the reverse car parking. This system is automatically activated when you reverse gears. Small sensors are located at the rear of the car which send and receive ultrasonic radio waves in the event of an approaching obstacle. There is an internal buzzer that gradually increases in frequency as you approach the object and displays the distance on the LCD screen.
Depending on the speed of the vehicle and its distance from the obstacle the car parking system warns the driver via audio or visual means about the possibility of a collision. Warning mainly depends on the speed and proximity of the obstacle. Warnings are deactivated when the vehicle exceeds a certain speed, and can be switched off for situations such as stop-and-go traffic.
Cars which are incorporated with a visual parking sensor system usually use a LCD or LED screen to display the distance of the approaching danger or object. The direction and distance from the obstacle is indicated by the location and strength of the warning symbols.
This is the most common form of car parking sensor system. The warnings are generally given via beeps or tones. Generally the frequency of beeps determines the level of danger. The beeps become faster as the obstacle starts coming closer to the vehicle. A continuous tone may be heard when the vehicle is extremely close, often warning a driver to stop immediately to avoid collision.