What Is a Security System and How Does it Work?

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Security systems detect entry into your home. After a brief delay to allow you to disarm the system, a siren blares and a professional monitor—if you subscribe to such a service—calls to make sure it's not a false alarm

Let's take a look at common security sensors, monitoring options, communication protocols, and more.

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What is a security system?

Security systems are networks of integrated electronic devices working together with a central control panel to protect against burglars and other potential home intruders.

A basic security system includes:

  • A control panel or base station with a separate keypad
  • Door and window sensors
  • Motion sensors
  • Glass break sensors
  • Security cameras

But there are plenty of other devices available to enhance your home's security, including smart home products and environmental sensors.

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How does a security system work?

Security components communicate their status to the control panel, and the control panel communicates to the monitoring station (if applicable—more on that below) and to your smartphone. 

Security communication protocols differ from system to system. Hardwired systems use electrical wires to connect all components to the control panel. Wireless security components communicate to the control panel through radio frequencies or a mesh network.

Control panels use Wi-Fi or cellular data to connect to your smartphone app and the monitoring center. Landline-based security systems are rare.

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A closer look at how common security components work

Control panel

The control panel is the computer that arms and disarms the security systems, communicates with each installed component, sounds the alarm when a security zone is breached, and communicates with an alarm monitoring company.

They typically feature a touchpad for easy programming and interaction. You'll enter your PIN to arm and disarm the system, but some can be armed with a voice command. You can also use a key fob to arm and disarm the system quickly, or use a smartphone app to control the system from anywhere in the world—literally.

Door and window sensors

Door and window sensors—also called contact or entry sensors—are comprised of two parts. They're installed right next to each other on a closed door and door frame (or closed window and window frame). One part of the sensor detects a magnet in the second part. As soon as the magnet is moved out of range (i.e., the door or window opens), the sensor communicates a breach to the control panel.

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Motion sensors

When armed, motion sensors protect a given space by creating an invisible zone that cannot be breached without sounding an alarm. Common motion sensor technology includes ultrasonic waves and passive infrared technology.

Motion sensors are typically used to protect hallways, rooms with multiple windows or entry points, and areas with an open floor plan. 

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Glass break sensors

Glass break sensors protect rooms with multiple windows. They work by sensing either the vibration or sound of breaking glass. Sound-based glass break sensors are more common. 

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Security cameras

Available in both wired and wireless configurations, the typical security camera only records footage when motion is detected. 

Most security cameras connect to a smartphone app via Wi-Fi so you can view live footage at any time. Recorded footage is stored in the cloud or on a microSD card. 

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What happens when an intrusion occurs?

What your security systems does in the event of an intrusion depends on whether you have professional monitoring or not. 

Professionally monitored security systems

If your security system is professionally monitored by an alarm company, they are alerted when a security problem arises in your home. A trained security expert might attempt to communicate with the homeowner via the control panel if it’s set up for 2-way voice communication, or will call the emergency contact number listed on the account.

These types of security systems communicate with the monitoring company in one of several ways, including:

  • Over existing home phone lines, which continue to work during power outages when battery backup is in use.
  • Wirelessly through cellular radio frequencies like cell phones use, which also continue to work during power outages when battery backup is in use.
  • Voice over Internet Protocol (VoIP), which typically doesn’t work in a power outage.
  • Via the Internet, which also typically does not work in a power outage.

In the event of an actual emergency, the monitoring company will notify the appropriate emergency response personnel in your area. 

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Self-monitored security systems

There are plenty of DIY security systems available today that don’t include professionally monitored services. In the event of a home intrusion when this type of security system is installed, a high-decibel alarm sounds (provided one is installed). Contacting police, fire, or other emergency response personnel must be initiated by the homeowner by dialing 911.

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Cathy Habas
Written by
Cathy Habas
With over eight years of experience as a content writer, Cathy has a knack for untangling complex information. Her natural curiosity and ability to empathize help Cathy offer insightful, friendly advice. She believes in empowering readers who may not feel confident about a purchase, project, or topic. Cathy earned her Bachelor of Arts degree in English from Indiana University Southeast and began her professional writing career immediately after graduation. She is a certified Safe Sleep Ambassador and has contributed to sites like Safety.com, Reviews.com, Hunker, and Thumbtack. Cathy’s pride and joy is her Appaloosa “Chacos.” She also likes to crochet while watching stand-up comedy specials on Netflix.

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