Two Types of Car Alarms

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Car alarms are electronic devices installed in the vehicle in an attempt to discourage theft of the vehicle itself, its contents or both.

Car alarms work by emitting high-volume sound when the conditions necessary for triggering are met, as well as by flashing some of the vehicle’s lights and notify the car’s owner via a paging system and interrupting single or multiple electrical circuits necessary for the car to start.

Car alarms can be divided into two categories;

  • Before Market Alarms

OEM (built into the vehicle at the factory): Before market (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.

Almost all OEM alarms are typically armed and disarmed with the vehicle 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 open 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 often vehicles equipped with a key based immobilizer and an alarm, the combination of the world key code and the ignition disarms the system.

  • After Market Alarms:

Like OEM alarms, after market systems are usually armed and disarmed via remote. Usually they do not have provisions for external disarming form the key cylinder, but will typically have over ride switch mounted in a hidden location.

The simplest alarm would have a switch on the driver’s door and it would be wired so that if someone opened the door the siren would start wailing. You could implement this car alarm with a switch, a couple of pieces of wire and a siren.

  • Most modern car alarm systems consist of:
  1. An array of sensors that can include switches, pressure sensors and motion detectors.
  2. A siren, often able to create a variety of sounds so that you can pick a district sound for your car.
  3. A radio receiver to allow wireless control from a key fob.
  4. An auxiliary battery so that the alarm can operate even if the main battery gets disconnected.
  5. A computer control unit that monitors everything and sounds the alarm-the brain of the system. The brain is most advanced systems are actually a small computer.

The brain’s job is to close the switches that activate alarm devices-your horn, headlights or can installed siren-when certain switches that power sensing devices are opened or closed. Security system differs mainly in which sensors are used and how the various devices are wired into the brain.


You can contact Eureka Technical Services Limited for more information!

We are a security and safety limited company focused in ensuring road safety has all that you need to ensure road safety! Contact us for all your road safety needs: Speed Warning Systems, Car Alarms, Digital Speed Governor with Record and Online Tracking and Vehicle Tracking System.

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Eureka Technical Services Limited

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