Parking Sensors & Cameras
Parking sensors emit an audible signal when reverse gear is engaged this gets more strident and continuous as you approach an obstacle. A Visual indicator going from green to red can be added.
A camera can also be used, so you can see objects such as children which cannot be seen from inside the vehicle especially with a 4 x 4 or Van. These are also often used to assist when hitching a trailer since you can see the tow-bar and manoeuvre accordingly.
There are many types of camera and the type used will depend on the vehicle. Sometimes these can show the picture on the existing screen in the car or, alternatively, on a dash-mounted screen or a rear mirror screen.