The term back-up horn refers to an extra horn (in addition to the normal one) that is independent of your car’s electrical system and forms part of the Anti-Theft Alarm System. If an unauthorised person attempts to enter your car, the Anti-Theft Alarm System responds by activating the back-up horn. In addition, the hazard warning flashers are switched on. The 30-second alarm can be turned off by opening the car.
Furthermore, if you lock or unlock your car by means of the remote control, the back-up horn confirms the action with a brief acoustic signal. However, this feature is not permitted in some countries, such as Germany, and can therefore be disabled electronically.