Car alarm
From Free net encyclopedia
A car alarm is a device installed in a car in an attempt to discourage theft of that car. Most alarms work by merely making a loud sound. Other alarms disable the ignition of the car, or send a signal to the owner (by means of a 1-way beeper) that his or her car is being disturbed.
Car alarms can be designed to be triggered by vibrations, tilting of the car (to prevent unauthorized towing), touching the car, the opening or closing of special switches (e.g. door contacts), sensing small but rapid changes in battery voltage (which might indicate an interior light going on, or the ignition circuit being activated), or using volumetric sensors such as ultrasound or infra red.
The vast majority of car alarms which sound are accidental. They are caused by the passing of large trucks, the vibration of thunder or people touching the car innocently.
Since most car alarms are accidental, most people in American cities are numbed to the sound of alarms, and do nothing to prevent theft. The New York City Police Department claims that car alarms are actually making the crime problem worse (see their booklet called "Police Strategy No. 5: Reclaiming the Public Spaces of New York," City of New York, New York, 1994) because since nothing is done about the alarms, the general impression is that no one cares about the neighborhood.
Because of the large number of false alarms with car alarms, many vehicle manufacturers no longer factory fit simple noise-making alarms, instead offering silent—but effective—vehicle immobilizers. Alternatively, an aftermarket vehicle tracking system can enable the police to trace stolen vehicles, making it more effective than a factory immobilizer. Most tracking systems require the user to pay a recurring fee, whereas factory immobilizers are included in the purchase price of the vehicle. Both classes of devices deter someone from taking the vehicle without consent but do not cover theft from, or vandalism of, the vehicle.
Yet another class of security covers aftermarket car alarms that include 2-way paging controllers. Two-way pagers have remote control functions built-in, allowing the user to arm and disarm the alarm while informing the user of threats made to the vehicle. Some 2-way systems have an LCD icon display that can pinpoint the actual part of the vehicle being threatened. Many two-way pagers can also alert the user with beeps or silent vibration.