The advanced key allows the driver to keep the car key in their pocket when unlocking and starting the automobile. The key is identified via a proximity sensor in the car door and a radio pulse generator in the key housing as soon as the driver is within approximately 1.5 metres of the vehicle. The vehicle is automatically unlocked as soon as the door handle (or trunk lid) is actuated. Some luxury vehicles have hidden the key cylinder behind a cover for styling. You don't need a key cylinder unless the batteries on the key fob are dead. For when this happens, there is a conventional key hidden inside the key fob. Cars usually have a backup key cylinder on the driver's door or even also on the passenger door. Cars with hidden key cylinders have covers that can be removed to use the cylinder if necessary, and can be replaced after. The advanced key system also means that the steering is released and the ignition is activated electronically and without inserting the key in the ignition. The driver must have the key with him inside the car before the engine can be started by pressing down on the brake pedal and then either pressing a starter button or twisting an ignition switch, depending on the car model. When leaving a vehicle equipped with advanced key, it suffices to merely press the small locking button on the driver's door handle in order to lock the vehicle.