The alarm is an electronic alarm fitted in a car, designed to deter would be thieves from stealing the car, or any belongings kept within the car. The alarm is, therefore, a useful piece of kit in providing some peace of mind when leaving your car parked unattended. Car alarms are often fitted into the car by the manufacturers at the time they are built but there are also aftermarket alarms available, which can be fitted after the car has been built.
The alarm works by producing a very loud, often piercing, noise which is designed to stop the thief, which is triggered by certain factors. Sometimes the sound produced will be a siren or maybe the car horn will sound constantly or in some cases a pre-recorded voice gives out an alert message. In some cases, the lights will flash on your car as an extra alert. Advanced car alarms will be programmed to send a message via text or pager to alert the car owner that the alarm has been activated. Certain alarms will shut down the electrics on the car when the alarm is sounded, therefore immobilizing the vehicle, so that it can't be accessed or started. What actually sets the alarm off will depend on the make and model of the alarm. Aftermarket alarms are usually universal, meaning they are made to work with all makes and models of car, but can be adjusted or configured to individual requirements which means the driver can choose to activate certain alarm triggers and disarm other triggers if they wish. Part of the car's safety system are the locks on the doors. Some complete vehicle lock sets operate with a remote keyless central locking system which means by pressing a button on a remote control the locks included in the set will lock or unlock and this can also activate or deactivate the alarm system on the vehicle.
Most alarms have an electronic sensor, known as a shock sensor, and a control unit, which connects to the battery of the car. When the alarm is activated, it is set off by vibration picked up by the shock sensor, for example, or by a change in voltage caused by a door being opened or the ignition being turned on, for instance, which the alarm recognizes as an intrusion. It is common for this type of alarm to trigger accidentally, however. Some alarms will have the option to add extra sensors if desired, such as a specific sensor which is triggered by the sound of glass breaking; motion or proximity sensors which detect movement in or outside the car; an anti-pinch sensor, which detects when something obstructs the window or someone tries to break into the car through the window; or a tilt sensor which recognizes when the car is being towed away. These types of sensor are usually less likely to be triggered accidentally because you can control and adjust the settings of the sensors making them less likely to pick up a false trigger. Proximity sensors, however, are renowned for triggering accidentally if they are set to a particularly sensitive setting, often picking up on someone walking close to the car and identifying this as an intruder. Alarms can also be triggered incorrectly from other loud sounds, such as loud music with a heavy bass or excessively loud exhaust noise from other vehicles, for example. The problem with false alarms is that people get so used to hearing car alarms sound, that complacency can strike and people tend to ignore the sounding alarm, assuming it is a false alarm, when an actual theft could be taking place.
If the alarm is not working properly and keeps sounding when it shouldn't, it could be that the settings on the sensors need to be adjusted. It could, however, mean that the alarm has not been fitted properly or is faulty and will need to be replaced.