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Car Alarm

A car alarm is an electronic device that consists of one or more sensors that are connected to some type of siren. Read up more on different types of car alarms. Madrasi.Info has hundreds of informative pages for the Car lovers.
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A study shows that one car is stolen every 24 seconds in the United Sates; the story is either the same or worse in every other country. The priority of all car owners is the safety of their car and its components. They would go an extra mile and spend a little more to make certain their car is safe from theft.

A car alarm is an electronic device that consists of one or more sensors that are connected to some type of siren. Car alarms produce a high-volume sound when the source is triggered. The noise from the alarm is produced by a siren, the vehicle's horn, klaxon, pre-recorded verbal warning or a combination of any of the above.

In a few cars, lights are activated as and when the car alarm is activated. In few other vehicles, the owner is notified through a pager message. In a few other car models, the electronic circuits required to start the vehicle gets disrupted once the car alarm is activated.

Understanding car alarms

Passive car alarms automatically get switched on as soon as the ignition is turned off. On the other hand, active car alarms need to be manually enabled and disabled.

OEM alarms:

OEM car alarms are armed and disarmed through the car's keyless door remote. In most cars, the key cylinder placed in the driver's door or the front passenger door activates the switches. Once a key is placed in the keyhole of the car the car alarm gets armed or disarmed.

Aftermarket car alarms:

They are similar to OEM alarms and are armed and disarmed through a remote. Instead of a key cylinder an overriding switch is placed in a hidden place.

Car alarms triggers:

Car alarms have triggers depending on the model of the car. Trigger in OEM alarm varies according to the model of the car but after market car alarm has a similar type of trigger.

OEM alarm triggers:

These alarms monitor the door, trunk or hatch of the car for unauthorized entry. Pin switches, mercury switches or micro switches are built-in right into the latch. In a few cars, alarm switches are built-in into the door lock mechanism itself. Other types of OEM alarm triggers get activated if the hood of the car is opened or when the ignition of the car is turned on. In a few cars the car alarm will be triggered if the shock sensor of the vehicle is triggered. The shock sensor gets triggered if there is a considerable impact on the body of the vehicle.

Aftermarket alarm triggers:

The simplest alarm triggers will have a single piece unit with a control module and a siren. The shock sensor in this unit is triggered either by the vibration or sudden voltage change in the input. Other types of triggers are optional sensors that get triggered when the vehicle is tilted while there is motion inside or outside the vehicle, or when the glass of the vehicle is broken.

Functioning of car alarms

To warn away:

Car alarms will stop any person from fiddling with the car. Multi-stage shock sensors, voice modules with microwave sensors and LEDs are used for this purpose.

To alert:

Car alarms focus attention to a possible theft of the car or the components of the car. Flashing lights, strobe lights, pain generators, sirens, smoke or voice response, pager or cellular interface is used to alert the owner from a distance.

Systems used in car alarms

Earlier car alarms made a noise when the door of the car was opened; this was the simplest system available. Modern day car alarm systems consist of highly sophisticated systems like the ones listed below:

  • The simplest type of car alarm has a switch located in the driver's door; this is wired to a siren. Once the door is opened, the siren produces a loud noise. This is the conventional car alarm.
  • Different types of sensors include pressure sensors, motion detectors, switches etc.
  • An auxiliary battery is used so that it can activate the car alarm even if the main battery fails.
  • Radio receivers permit wireless control from a key fob.
  • The most sophisticated component is the computer control unit; this monitors all the functions and triggers the car alarm.

Car alarm features

Air horns :

They are used inside and outside the car to generate more noise when the interior of the car is tampered with.

Ignition/starter kill:

The ignition/starter will get disconnected once the alarm is armed.

Pin switches:

This switch either connects or disconnects the electrical connection once that particular area is opened thus sending a trigger signal to the brain of the alarm. This switch is usually used in the hoods, doors or trunks of the car.

Microwave detectors:

It is a kind of proximity sensor, as it will get activated if an object enters the sensor's area of protection.

Emergency disarm switch:

The alarm will be disarmed in emergency by a hidden switch.


A signal is sent to the pager when the car alarm is triggered.


Additional lighting is enabled to draw extra attention once the alarm is triggered.


This helps to track the vehicle if the vehicle is stolen by chance.

You can choose options like driver side alarm priority where you can unlock only your door without compromising on the safety of the vehicle.

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Car Alarm