The best models flash the headlights and honk the horn in addition to sounding a siren. After years of false alarms, people have stopped paying attention to alarms. There is no statistical evidence that they reduce auto theft. Some car manufacturers have pre-installed electronic immobilizing systems that allow the vehicle to operate only with a correctly coded key. These interrupt your car's ignition systems when an incorrect key or no key at all is used to start the car.
Systems are easy to use and reliable.
Because they're invisible to thieves, inexperienced criminals will tear apart your steering column before discovering this disabling feature. Unfortunately, your steering column will need replacement and you probably won't be able to start your car. There are a variety of services offered by each company, such as mapping services and vehicle-location if your car is stolen. Lo-Jack is currently available for use in 15 states and 20 major cities. At a quick glance, the thief doesn't know that the warning light is bogus and may go on to another vehicle rather than take a risk.