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How a Home Security System Works

Gloved burglar breaking into a house

When your home security system’s alarm sounds, it could mean one of many things. You could have an intruder in your home, or you could have a fire, a flood, or a carbon monoxide leak. You also could have simply forgotten to disarm the system. But whether it’s an emergency or a false alarm, a triggered alarm system can be stressful and unpleasant.

Understanding how your system works and what happens when an alarm is triggered can help you stay calm during a real emergency.

What Happens When My System is Triggered?

Graphic of ADT alarm being triggered

#1 Alarm Triggered

Your alarm system sounds when one of your sensors is triggered or you manually set off the alarm through your control panel or key fob remote. Depending on how your system is set up, one of two things will happen-either a high-decibel alarm will sound or a silent alarm will be sent to your ADT monitoring station.

ADT logo and twenty four seven phone icon

#2 ADT Notified

Your ADT monitoring station will be notified and a dispatcher will be alerted to a possible emergency at your home. ADT monitoring stations are staffed 24/7, so there is always someone ready to respond to your alarm.

Cell phone icon being called by ADT security

#3 Dispatcher Contacts You

Once a dispatcher is notified, they’ll contact you to verify if it is a legitimate emergency or a false alarm. Depending on the service and system you have, the dispatcher will contact you either through your control panel (using 2-Way Voice technology) or will call you on your home or cell phone to verify the situation.

ADT alarm being canceled

#4 Emergency Verified

Once the dispatcher contacts you, they’ll determine what is going on. If it is a false alarm, the dispatcher will cancel the alarm and will not notify your local emergency response team. If the dispatcher cannot contact you, they will assume there is an emergency.

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#5 Emergency Services Notified

If there is an emergency, the dispatcher will contact the local authorities, including police, fire, and emergency response team, depending on the type and severity of the situation.

Graphic of police arriving at ADT secured home

#6 Help Arrives

The emergency response team should arrive at your home shortly to help provide assistance and support to you and your family.

What Triggers an Alarm?

The majority of security systems come with wireless sensors that can be placed in strategic locations around your home, like on doors or windows and in living rooms and bedrooms. When these sensors are triggered, they send a signal to your security system control panel, which will alert your ADT monitoring station.

Here are some common sensors that can be triggered in the case of an emergency.

Graphic demonstrating how sensor is triggered

Door/Window Sensors

Magnetic door/window sensors are made up of two small magnetic pieces; one is mounted to the top of the door or window frame, while the second is placed directly on the door or window. Vanishing sensors can be placed inside the door/window and inside the frame so no one knows they are there. The two sensor pieces are in contact with each other while the door/window is closed. When they are opened, the sensors separate and an alarm is triggered.

Graphic showing how motion sensor is triggered

Motion Sensors

The most common type of motion sensor is the infrared sensor. These sensors emit infrared light and are triggered when they detect body heat. They identify intruders by comparing the heat of inanimate objects with the heat of anything moving in its field of detection–like a human. Many motion sensors are designed with Pet Immunity to avoid false alarms being triggered by small pets in the home.

Graphic showing how glass break sensor is triggered

Glass Break Sensors

There are two types of glass break sensors: shock sensors and acoustic sensors. Shock sensors detect vibrations when glass breaks or shatters, while acoustic sensors are designed to detect the exact sound waves of breaking glass. Both are efficient, but the acoustic sensors can monitor a wider area, such as large bay windows or sliding glass doors.

Graphic showing how smoke detector is triggered

Emergency Sensors

Emergency sensors are an added layer of security most people don’t always think about. Flood sensors will help to detect and notify you of any moisture in your home caused by flooding, burst pipes, or any other water-related emergency. These sensors should be installed in leak-prone areas of the home, like behind the water heater or under sinks. Carbon monoxide detectors will help alert you when high levels of CO are detected in your home, and smoke sensors detect smoke and spikes in temperature.

ADT key fob with panic button outlined

Manually Trigger the Alarm

Most alarm systems can also be triggered manually in case of an emergency. The alarm can be set off by pushing the panic button on your control panel or your key fob remote.

How Do I Arm/Disarm My Security System?

Arming and disarming your security system is simple–as long as you have the code.

Person using ADT keypad


Stay mode will turn off all internal motion sensors but keeps door and window sensors active. You’ll be able to move about the house with the peace of mind that you’ll be notified if any entry points to your home are breached.

Away mode activates your entire system. This is the mode you will use whenever you leave the house and know that no one else is inside.

You can arm your system by pushing the STAY or AWAY buttons on your control panel or using your key fob remote, which is a real convenience and can be used from up to 50 feet away.

Graphic of person disarming alarm with key fob


Although each security system is different, you can disarm your system by choosing the Disarm or Stay mode on your control panel and entering your security code or using your handy-dandy key fob remote.