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How Do Alarm Motion Sensors Work?

20 Aug 2019

While motion detectors are undoubtedly an integral part of your security system, few people outside of the industry understand how these devices differentiate between and intruder and a person who is meant to enter the home.

This article will discuss exactly how motion detectors work and when you should install them in your home.

How Motion Detectors Work

There are a number of options available when it comes to picking a motion sensor for your home. Most of today’s motion sensors are wireless, electronic, and use either active or passive sensors.

Active Sensors

Active Sensors are also referred to as radar-based motion detectors and they work by emitting ultrasonic sound waves. When an interference in the sound waves is detected, the sensor will then send a signal to sound an alarm.


Some active sensors will activate a light when tripped or even open a door as opposed to sounding an alarm. A professional security consultant will help you to determine what makes the most sense for you and your home.


If you've ever seen a spy movie where the main character has to pass through a bunch of invisible laser beams (revealed by chemical fog) to infiltrate a facility, you know what photosensors are. These are commonly used in driveway alarm systems.


Photosensors use laser beams and light sensors to detect intrusion and will sound an alarm when a change in light is detected. Some systems even illuminate a light beam on the intruder when he or she is detected.

Passive Infrared Sensors

Also known as PIR sensors, this is the type of sensor that is most commonly chosen to protect residential homes due to its cost-effectiveness and ease of use. These sensors detect infrared energy that is released from the body heat radiating off of humans and animals.

motion sensor walk2

PIR sensors are intuitive and can come with a variety of features such as a 90-degree look down, so that no intruder will be able to sneak underneath the sensor's range of vision.

Set up and Installation

While you may be able to figure out how to set up your motion detectors on your own, many people benefit from getting the help of a professional to ensure the equipment is set up correctly. Should you decide to self-install, we can help guide you through that process over the phone.

Where Should Motion Detectors be Installed?

The first place to consider is outside your front door as most intruders will try to gain access to the front door before trying to open your windows.

Second, we suggest placing them in hallways that an intruder would have to travel down as they make their way towards their primary target: the master bedroom.

Motion detectors are not only used for keeping intruders out; if you have little ones at home that you want to keep away from hot or dangerous areas, you can install a self-monitored motion detector that will notify you when the device detects any movement in the off-limits part of your home.

A professional installation team will be able to listen to your needs and concerns and then implement a plan to make sure that your detectors are installed in the proper places that suit your needs.

Do I Really Need Motion Detectors?

The benefits of having motion detection technology in your home are numerous. When used in conjunction with other security measures like glass break detectors, motion detectors are highly effective.

You can never be too cautious when it comes to protecting your family and since we can't physically be everywhere at once, motion detectors provide an extra layer of security and peace of mind.

The Ultimate Home Security Guide

A comprehensive list of steps you can take to protect your home and your loved ones.

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Alarm New England is located at 2 Park Plaza #305 in Boston. We are located about 10 minutes walk from Park St Station. We are open Monday – Friday 9:00am – 5:00pm. For additional questions you can call us at (857)445-4010 or you can find us on Trustpilot.

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