A car alarm is a device that can be found on some cars and similar vehicles that emits some form of signal in response to events that may be indicators of car theft. The signal sent by such devices can vary a great deal, and may include audible signals such as sounding of the car horn and other alarms such as secondary horns and sirens. Some of these devices can instead send a digital signal to a secondary receiving system, such as a text message to a person’s wireless telephone or computer messaging service. A car alarm may be somewhat effective at deterring potential car thieves, though some evidence shows that other devices, such as immobilizers, are more useful for this purpose.
There are a number of different car alarm manufacturers that produce a wide array of vehicle alarms available for purchase and installation. In general, however, these devices can be divided into two categories: factory-installed devices and aftermarket car alarms. A factory-installed car alarm, also known as an original equipment manufacturer (OEM) device, is included when a car is built and provided by the manufacturer. These devices can often be preferable due to a number of features they can include.
Factory car alarms are built into the entirety of the car itself and so can often be more sensitive to real threats of theft. For example, a factory-installed car alarm can include sensors built into the door locking mechanisms to detect when a car is unlocked. Aftermarket alarms, those installed after a car is purchased, are typically added to existing systems and so tend to be less sensitive. These types of alarms are often those that go off at times other than when appropriate and may lead to frustration from those subject to the resulting noise.
This high tendency for car alarm systems to go off when no actual theft is occurring has led to many of these systems losing popularity. A number of studies have shown that most people ignore the sound of a car alarm, and so it does not necessarily present any deterrence to criminals. Immobilizers, on the other hand, are security systems that prevent a car from starting without a specific key or device being present to start the vehicle. These types of devices have, so far, shown greater effectiveness in preventing theft, and have become increasingly popular as OEM devices.