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A car alarm is an electronic device installed in a vehicle in an attempt to discourage theft. Car alarms work by emitting high-volume sound (usually a siren, klaxon, pre-recorded verbal warning, the vehicle's own horn, or a combination thereof) when triggered or when circuit is breached. Image File history File links Broom_icon. ... Karl Benzs Velo model (1894) - entered into the first automobile race An automobile or motor car (usually shortened to just car) is a wheeled passenger vehicle that carries its own motor. ... Everyday instance of theft: the bike which fits on this wheel has disappeared. ... For other uses, see Alarm (disambiguation). ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... It has been suggested that Fire siren be merged into this article or section. ... Audio sample: Klaxon ( file info) — A sample of a submarine dive klaxon used by United States Navy submarines during World War II Problems listening to the file? See media help. ...

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 , infrared or microwave. Oscillation is the variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... Heavy Tow truck A tow truck, also sometimes called a wrecker, is a vehicle used to take disabled motor vehicles off a roadway to another location in case of breakdown or collision, or to impound illegally parked vehicles on public or (more commonly) private property. ... Symbols representing a single Cell (top) and Battery (bottom), used in circuit diagrams. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Ultrasound is a form of cyclic sound pressure with a frequency greater than the upper limit of human hearing, this limit being approximately 20 kilohertz (20,000 hertz). ... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. ...

Many times a car alarm can be triggered accidentally. This may be caused by the passing of large trucks, the vibration of thunder or people coming into contact with the vehicle, triggering the alarm sensors. Some sensores may need adjustment in order to prevent false alarms.^{[citation needed]} The driver of this DAF tractor with an auto-transport semi-trailer truck prepares to offload Å koda Octavia cars in Cardiff, Wales For other articles with similar names, see Lorry (disambiguation) and truck (disambiguation). ... Thunder is the sound made by lightning. ...

Since many car alarms are triggered accidentally, 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 nothing is done about the alarms, the general impression is that no one cares about the neighborhood.^{[citation needed]} The New York City Police Department (NYPD) was created in 1845 and currently is the largest municipal police force in the world with primary responsibilities in law enforcement and investigation within the five boroughs of New York City. ... New York, New York and NYC redirect here. ... NY redirects here. ... Year 1994 (MCMXCIV) was a common year starting on Saturday (link will display full 1994 Gregorian calendar). ...

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—immobilizers.^{[citation needed]} Alternatively, an aftermarket vehicle tracking system can enable the police to trace stolen vehicles. Most police tracking systems require the user to pay a recurring fee, whereas factory immobilizers are included in the purchase price of the vehicle. GPS locating systems enable the owner of the vehicle to lock and unlock, track, and disable the starter of the vehicle online. Other additional options allow the user to receive messages if the alarm is set off or if the vehicle breaches a specified speed or boundary. GPS systems are usually not paid monthly but locates are purchased. Both classes of devices deter someone from taking the vehicle without consent but do not cover them from theft, or vandalism of, the vehicle. An immobiliser is an electronic device fitted to an automobile which prevents the engine from running unless the correct key (or other token) is present. ... A vehicle tracking systems is an electronic device installed in a vehicle to enable the owner or a third party to track the vehicles location. ... Vandalism is the conspicuous defacement or destruction of a structure, a symbol or anything else that goes against the will of the owner/governing body. ...

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. Aftermarket is an umbrella term for the collective network of vendors who design and sell vehicular components that are intended to replace the stock manufacturers parts in order to alter the appearance or performance of the vehicle. ... Reflective twisted nematic liquid crystal display. ... Nuvola icons for KDE are available in PNG format, which come in six sizes, and SVG format, which is scalable On computer displays, a computer icon is a small pictogram. ...

In popular culture

In modern times, it is frequent for car alarms to be used in movies or TV shows to add elements of comedy or drama to a particular scene, such as a character accidentally triggering one and being startled by the resulting noise, or having one set off when a catastrophic event happens to the car and/or in the immediate vicinity.

See also

• Immobilisers
• Anti-hijack system
• Vehicle tracking system

An immobiliser or immobilizer is an electronic device fitted to an automobile which prevents the engine from running unless the correct key (or other token) is present. ... This article does not cite any references or sources. ... A vehicle tracking systems is an electronic device installed in a vehicle to enable the owner or a third party to track the vehicles location. ...

External links

• Article from Highway Loss Data Institute
• Car Alarm Wiring Guides