How Home Security Devices Function

Intrusion prevention begins with simple measures like keeping all doors and windows locked, even when you are home. To seasoned burglars, however, a locked door or window is only a minor inconvenience. A determined intruder will not hesitate to smash a window or kick in a door. A few seconds' effort and a little noise, and he will be inside, pilfering your valuables or even threatening your life.

According to studies conducted by the United States Department of Justice, more than 2.5 million U.S. households experience a burglary or criminal trespass incident each year. You can catch perpetrators in the act—or deter them altogether—by installing an integrated security system comprised of multiple intrusion detection systems.

These include door/window sensors, glass break sensors, motion sensors, and garage door tilt sensors. This blog provides an overview of how these home security devices function. It also explains how they work together to protect your property and loved ones.

Another study by the Justice Department found that doors were the most common way for burglars to gain entry, with windows not far behind. Resourceful intruders often make short work of door or window locks using either practiced finesse or brute force. This is where door/window sensors come in. These wireless, battery-powered devices activate when someone opens something that is supposed to be closed.

A door/window sensor typically is comprised of two parts. The first is a sensor attached to the door or window frame. The second is a magnet that sits across from the first component on the door or window itself. The sensor unit contains an electrical reed switch with separated connectors. When the magnet rests directly adjacent to the sensor, it generates a closed electrical circuit, indicating to the system that the door or window is closed.

When someone opens the door or window, the action separates the two components. This breaks the electrical circuit, triggering the sensor. If the unit is part of a Frontpoint integrated security package, it will alert the system hub using wireless Z-Wave technology. The panel then sounds an audible alarm and can signal the homeowner with a mobile notification—as well as alert a professional monitoring service.

Unmonitored, unintegrated door/window sensors usually just sound an alarm inside the house. This is better than nothing but does little good if no one is home. Monitored intrusion detection systems, like those offered by Frontpoint, provide a critical connection to outside help, whether occupants are inside and in danger, or they’re on the other side of the world.  

Once an alarm is triggered, security professionals call you twice. If no one answers, an owner does not indicate a false alarm, or an incorrect passcode is given, the monitoring center sends local emergency responders immediately. If the system is also equipped with security cameras, an absent homeowner can visually inspect the situation via a mobile app.

In addition to defending your loved ones and property from intruders, door/window sensors can also secure your residence in other ways. They can prevent unauthorized entry into liquor or gun cabinets. They can also raise an alert when children enter a forbidden area or attempt to exit the residence. They provide similar safeguards in households with people living with dementia who tend to wander.

And security systems provide even more protection when door/window sensors are paired with another form of intrusion prevention: the glass break sensor.

Ideally, a fully secured dwelling will feature door/window sensors on every exterior door and accessible window. This may be prohibitive for cost-conscious individuals, especially if the residence has numerous windows. And regardless of budget, some rooms with a lot of glass openings—such as sliding doors—are better protected when glass break sensors complement door/window sensors.

These devices monitor entire rooms or sections of the dwelling for the sound of shattering glass. Thus, even if some windows are not equipped with an intrusion sensor, smashing just one pane of glass will trigger the glass break sensor.

Frontpoint’s Glass Break Sensors are acoustically tuned to listen for the distinct sound frequencies produced by breaking glass. They detect these sounds and notify the intrusion detection system’s control hub from distances up to 100 feet. The control panel then alerts the homeowner and/or the professional monitoring service (the latter if the system is armed). Frontpoint sensors are also sensitive enough to tell the difference between the sound of a smashed windowpane and ordinary household glass breakage. So, you won’t have to worry about triggering a false alarm when someone drops a glass of water.

Glass break sensors work best when they’re mounted on walls and ceilings. They need a clear line of sight to glass doors or windows so they can do their job correctly. If there are no walls or furniture between the sensors and the glass, they can monitor all windows and glass doors within 20 feet in any direction. For best results, the sensors should be mounted at least 4 feet from the glass.

Despite the substantial protection offered by door/window sensors and glass break sensors, seasoned breaking-and-entering artists may still find ways to get inside undetected. Perhaps the battery ran out on another sensor, and a user neglected to replace it. Or maybe the intruder found the one unlocked window you didn’t protect with a door/window sensor.

In other instances, the problem may not involve an intruder at all. Families with small children must also be on guard. Kids may stray into portions of the home with hazards like steep stairways or power tools. A motion sensor will let you know that someone is where they shouldn’t be.

Just like their name suggests, motion sensors detect movement. The sensor may sound an audible alarm or, if it is integrated with a smart security system, send a mobile notification to the homeowner. If the sensor is linked to a monitored security system, it can also notify the monitoring center, which will send help if necessary.

There are two primary varieties of motion sensors—active and passive. Active motion sensors emit microwaves, sound vibrations, or some other form of energy. This beam actively searches for movement in a manner similar to radar or sonar. Active sensors are the most sensitive form of motion sensor and are used for applications like automatic doors or safety devices. They detect the smallest movement. This may sound desirable, but active sensors are also highly prone to false alarms. They are likely to activate when pets stroll through the room or even when a flying insect gets inside.

Passive motion sensors are better suited for home intrusion detection and prevention. They use infrared technology that detects changes in a room’s thermal environment. Specifically attuned to the amount of heat typically generated by humans, passive infrared sensors (PIR) usually ignore the movements of insects, inanimate objects, and even pets under 40 pounds. This significantly reduces the potential for false alarms—and they have a longer battery life and a lower price tag than active sensors.

Motion sensors work best when installed in corridors and high-traffic areas that intruders are likely to pass through while heading for key areas—the master bedroom, rooms with electronics or valuable items on display, etc. Likely entry points such as front foyers are also a good bet.

The sensors are usually better at detecting motion that crosses their beams, as opposed to someone approaching head-on. For this reason, it is best to install them high on the sides of hallways and other common passages. Avoid using them near heat sources like fireplaces or in hot spaces like attics or outdoor garages; the ambient heat in these areas can reduce the sensors’ effectiveness or even help trip them.

When securing entry points, don’t forget the garage. If an intruder manages to open this door, or if someone in the family leaves it open accidentally, it’s game on. The perpetrator will now have unfettered access to cars, tools, bikes, lawn equipment, or anything else you keep there. If it is an attached garage, he’ll also have access to your residence.

Garage door tilt sensors provide another form of intruder prevention by alerting you when the door tilts more than 45 degrees. If the device is tied to a smart security system, the battery-operated sensor will send you a remote notification, and it can alert the monitoring center if you armed the system. Plus, say goodbye to that frustrating thought as you drive away: "Did I forget to close the garage door?"

Frontpoint’s Garage Door Tilt Sensor should be installed on the highest panel of the garage door so that it can get an accurate read on the door’s angle of pitch.

We’ve already discussed the individual contributions each of these devices make to your intrusion prevention plan. But intrusion detection sensors really become powerful when they work together to provide layered protection.

As noted, glass break sensors back up door/window sensors by providing coverage for doors and windows not equipped with sensors. They also provide coverage for larger glass doors and windows, which intruders may smash and step through without opening. And if an intruder manages to gain entry without triggering a door/window sensor, a garage tilt sensor, or a glass break sensor, motion sensors will detect their presence.

Intrusion detection sensors can also work in harmony with other components of a smart home network. For example, motion detectors can turn off smart lights and lower a smart thermostat when the house is empty. You can also set motion sensors to turn on lights automatically when you need them—like that hard to reach bulb over the dark basement stairs. And door/window sensors can be placed on just about anything that opens or closes, giving you precise protection over sensitive areas. Plus, they can be programmed to turn on smart lights or command other devices when they are tripped.

But the primary purpose of an intrusion detection system remains identifying and stopping break-ins. And modern intrusions sensors that are integrated into a monitored smart security system do this incredibly well—locking down your home tightly against threats.

If you enjoyed this article, check out these other blogs:

• Flood Sensors, Heat Sensors, and Carbon Monoxide Sensors: The Facts
• Cool Ways to Use Door Sensors, Window Sensors, and More
• Exploring Home Security Camera Systems, Models, and Features

Frontpoint keeps families safer and more connected in their everyday lives. We've been revolutionizing the home security industry for over a decade. And we're just getting started. To shop monitored intrusion detection systems, check out our Security Packages. If you have questions or would like to discuss a quote, contact us at 1-877-602-5276.