Car alarm
Encyclopedia
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
in an attempt to discourage theft
Theft
In common usage, theft is the illegal taking of another person's property without that person's permission or consent. The word is also used as an informal shorthand term for some crimes against property, such as burglary, embezzlement, larceny, looting, robbery, shoplifting and fraud...
of the vehicle itself, its contents, or both. Car alarm
Alarm
An alarm device or system of alarm devices gives an audible or visual alarm signal about a problem or condition.Alarm devices include:* burglar alarms, designed to warn of burglaries; this is often a silent alarm: the police or guards are warned without indication to the burglar, which increases...
s work by emitting high-volume sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
(usually a siren, klaxon, pre-recorded verbal warning, the vehicle's own horn, or a combination thereof) when the conditions necessary for triggering are met, as well as by flashing some of the vehicle's lights, and (optionally) notifying the car's owner via a paging system and interrupting various electrical circuits necessary for the car to start.
Features
Car alarms should not be confused with immobilizers; although the purpose of both may be to deter car theft, they operate in a dissimilar fashion. An immobilizer generally will not offer any audible or visual theft deterrence, nor require any additional input from the driver than from the driver of a non-immobilizer car.Car alarms can be divided into two categories:
- OEMOriginal Equipment ManufacturerAn original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
(built-in to the vehicle at the factory) - AftermarketAftermarket (automotive)The automotive aftermarket is the secondary market of the automotive industry, concerned with the manufacturing, remanufacturing, distribution, retailing, and installation of all vehicle parts, chemicals, tools, equipment and accessories for light and heavy vehicles, after the sale of the...
(installed at any time after the car has been built, such as by the new car dealer, an auto accessories store, or the vehicle's owner)
Alarms come with a mix of features. Remote car alarms typically consist of an additional radio receiver that allows the owner to wirelessly control the alarm from a key fob. Remote car alarms typically come equipped with an array of sensors along with immobilizers and motion detectors.
Keyless remote car alarms are typically based on strong cryptography authentication methods:
- Radio receiver
- Immobilizer
- Motion detectorMotion detectorA motion detector is a device for motion detection. That is, it is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices that alert the user of the presence of a moving object within the field of view...
- Wireless USBWireless USBWireless USB is a short-range, high-bandwidth wireless radio communication protocol created by the . Wireless USB is sometimes abbreviated as "WUSB", although the USB Implementers Forum discourages this practice and instead prefers to call the technology "Certified Wireless USB" to distinguish it...
OEM alarms
Almost all OEM alarms are typically armed and disarmed with the vehicle's keyless entry remote. On many vehicles the key cylinders in the driver or front passenger door activate switches, so that when a key is used in the door the alarm will arm or disarm.Some vehicles will arm when the power door lock switch is pressed with the driver's door open, and the door is subsequently closed.
Some vehicles will disarm if the ignition is turned on; often when the vehicle is equipped with a key-based immobilizer and an alarm, the combination of the valid key code and the ignition disarms the system.
Aftermarket alarms
Like OEM alarms, aftermarket systems are usually armed and disarmed via remote. Usually they do not have provisions for external disarming from the key cylinder, but will typically have an override switch mounted in a hidden location.Alarm triggers
The individual triggers for a car alarm vary widely, depending on the make and model of the vehicle, and the brand and model of the alarm itself (for aftermarket alarms).Since aftermarket alarms are designed to be universal (i.e., compatible with all 12 volt negative ground electrical systems as opposed to one carmaker's vehicles), these commonly have trigger inputs that the installer/vehicle owner chooses not to connect, which additionally determines what will set the alarm off.
OEM alarm triggers
Generally, OEM alarms monitor the doors and trunk/hatch for unauthorized entry. On some vehicles this is done through pin switches, mercury switches, or microswitches integrated into the latch. On others, the doorlock mechanisms have switches built into them.Some OEM alarms additionally will trigger if the hood is opened, or if the ignition is turned on. Additionally a few systems have a shock sensor which will trigger upon a significant impact to the vehicle's body.
Aftermarket alarm triggers
The simplest aftermarket alarms are one-piece units with a siren and control module. Such a unit will typically contain a shock sensor and two wires (12 volt constant power and ground) which are connected to the car's battery. This type of alarm is triggered by vibrationOscillation
Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
transferred to the shock sensor, or by voltage changes on the input (the alarm assumes that a sudden change in voltage is due to a door or trunk being opened, or the ignition being turned on); however it is very prone to false triggers on late-model vehicles with many electronic control modules, which can draw current with the ignition off. For this last reason these alarms are increasingly becoming obsolete.
More sophisticated aftermarket alarms are wired in to the vehicle's electronics individually. Typically, these alarms have inputs for power and ground, as well as for positive- and negative-switched door open circuits, negative trunk and/or hood circuits, and ignition-switched circuits to detect the ignition being turned on; aftermarket alarms also usually have a shock sensor which may be built into the control module or external to it.
In addition, some aftermarket alarms have provisions for optional sensors which can sense the vehicle being tilted (this alerts against unauthorized towing), glass breakage (which can sometimes be done without an impact sufficient to trigger the shock sensor), or motion inside or immediately outside the vehicle (this is a concern on convertibles). Microwave detectors are frequently used for this
The sensors mentioned here are usually adjustable in order to avoid false alarms - for example a shock sensor will sometimes vibrate due to a loud noise in the area, or an accidental bump to the car from a passerby. This can cause the alarm to falsely sense an attempted break-in.
Some alarms will bypass some or all of the inputs at times by design. For example, Directed Electronics alarms have a feature called "Nuisance Prevention Circuitry" which ignores any input which has triggered 3 times within 1 hour, unless the car owner turns the ignition on to reset it.
Other alarms can bypass some of their inputs via a button combination on the remote, or when remote starting (if the alarm supports this feature).
Effectiveness
Since most car alarms are triggered accidentally (frequently because of high sensitivity settings), people often ignore alarms. The New York City Police DepartmentNew York City Police Department
The New York City Police Department , established in 1845, is currently the largest municipal police force in the United States, with primary responsibilities in law enforcement and investigation within the five boroughs of New York City...
claims that car alarms are actually making the crime problem worse because false alarms are so common that people simply ignore them.
Because of the large number of false alarm
False alarm
A false alarm, also called a nuisance alarm, is the fake report of an emergency, causing unnecessary panic and/or bringing resources to a place where they are not needed. Over time, repeated false alarms in a certain area may cause occupants to start to ignore all alarms, knowing that each time it...
s with car alarms, many vehicle manufacturers no longer factory-fit simple noise-making alarms, instead offering silent—but effective—immobilizers. Alternatively, an aftermarket vehicle tracking system
Vehicle tracking system
A vehicle tracking system combines the installation of an electronic device in a vehicle, or fleet of vehicles, with purpose-designed computer software at least at one operational base to enable the owner or a third party to track the vehicle's location, collecting data in the process from the...
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.
Frequently, false alarms occur because car alarm owners use high sensitivity settings. This is the main reason why loud bass frequency sound (loud music, other cars or motorcycles with loud exhaust systems, thunderstorms, etc.) can set off car alarms. The second possible reason is that some parts of the alarm system may be improperly installed. For example, a typical mistake is that the microwave sensor is not pointed upward as intended. A third possible reason is that the shock sensor is mounted to a bad surface, where all the vibrations caused by sound leads to shock sensor. If reducing sensitivity doesn't help, then another way to solve this problem is to place foam (or another soft material that absorbs vibrations/sounds) under the shock sensor or even covering/surrounding the whole shock sensor with foam. It can also become necessary to consider other methods to mount the shock sensor instead of using metal screws. Also, some of the window breakage sensors (the sensors that use microphones to detect broken windows) can false detect window breaking, for example, if someone detonates loud fireworks near the car, causing car windows to rattle.
Yet another class of security covers aftermarket
Aftermarket (automotive)
The automotive aftermarket is the secondary market of the automotive industry, concerned with the manufacturing, remanufacturing, distribution, retailing, and installation of all vehicle parts, chemicals, tools, equipment and accessories for light and heavy vehicles, after the sale of the...
car alarms that include 2-way paging controllers. Some 2-way systems have an LCD
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
icon
Icon (computing)
A computer icon is a pictogram displayed on a computer screen and used to navigate a computer system or mobile device. The icon itself is a small picture or symbol serving as a quick, intuitive representation of a software tool, function or a data file accessible on the system. It functions as an...
display that can pinpoint the part of the vehicle being threatened, and many alert the user with beeps or silent vibration.
See also
- ImmobiliserImmobiliserAn immobiliser or immobilizer is an electronic device fitted to an automobile which prevents the engine from running unless the correct key is present...
- Anti-hijack systemAnti-hijack systemAn anti-hijack system is an electronic system fitted to motor vehicles to deter criminals from hijacking them. Although these types of systems are becoming more common on newer cars, they have not caused a decrease in insurance premiums as they are not as widely known about as other more common...
- Vehicle tracking systemVehicle tracking systemA vehicle tracking system combines the installation of an electronic device in a vehicle, or fleet of vehicles, with purpose-designed computer software at least at one operational base to enable the owner or a third party to track the vehicle's location, collecting data in the process from the...
- Noise pollutionNoise pollutionNoise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...
- Long Range Acoustic DeviceLong range acoustic deviceThe Long Range Acoustic Device is a distance hailing device and non-lethal crowd control weapon developed by LRAD Corporation to send messages, warnings, and harmful, pain inducing tones over longer distances than normal loudspeakers....