planning an alarm systemFor millions of American households, one component of a home security plan is an alarm system, and there is evidence that these systems do make a difference: It is estimated that homes with security systems are one-third as likely to be burglarized as homes without them. Although part of the difference no doubt has something to do with location and other protections alarmed homes have in place, electronic alarm systems clearly matter. In addition, these systems help prevent fire damage, and some alert you (or a central monitoring agency) to power outages, water leaks, and other problems.

The discounts homeowners insurance companies offer households equipped with alarm systems are one indication of their value. Many insurers discount policies by two to 10 percent (most typically five percent) for homes with systems that have central station monitoring.

We recommend that homeowners first improve physical barriers to intrusion before considering alarm systems. Alarms can add protection against intrusions, but they also involve a significant expense and create some inconveniences. Should you get a system? We think it depends on several factors:

  • How well is your house physically secured against intrusions?
  • What is the incidence of burglary and other crime in your neighborhood?
  • Is your house regularly unoccupied during the day or evening? Do you take long vacations?
  • Do you have neighbors around most of the time to keep an eye on your house and call the police when they detect suspicious activity?
  • What are you likely to lose in a burglary? Is it replaceable? Is it insured for replacement value?
  • Are children, frequent houseguests, pets, or forgetful family members likely to trigger false alarms?
  • Does your family worry about break-ins?

Weighing Pros and Cons

Home alarm systems provide several kinds of protection. They notify you when doors and windows are inadvertently left open. Publicizing their presence—even the possibility of their presence—will deter some intruders. The sounding of an alarm will cause most intruders to flee and notify occupants of a present danger. The sounding of a siren will notify neighbors to call the police, and systems hooked up to a central monitoring station will notify the company to call the police.

Basic alarm protection should cover all exterior doors (including sliding glass doors) and any windows easily reached by intruders. The system should also activate a siren and/or notify a central monitoring station. Professional installation of a system meeting these criteria usually costs $1,000 to $2,000. Some companies offer steep discounts to customers who agree to sign long-term monitoring contracts. With these companies, you can get a basic system for less than $500 if you sign a three-year monitoring deal.

Moderately heavy alarm protection covers other points of potential entry, including second-story windows, attic doors, and skylights. It will also use motion detectors, pressure pads, and sensors on cabinets and bureaus to detect intrusions past the perimeter when the family is asleep or away. Such systems usually cost from $1,500 to more than $3,000.

Although the more time an alarm system remains in operation the more protection it provides, homeowners continually turn their systems off to prevent false alarms. Every time a person opens a monitored door or window, the system has to be reset, and motion detectors must be turned off when any human or pet is likely to enter their view. Living with an alarm system is at best an inconvenience, at worst enough of a hassle that homeowners don’t use it regularly.

False alarms are not merely inconvenient: They cause fear, erode neighbors’ goodwill, and, in many jurisdictions, result in fines. According to various estimates, 80 to 98 percent of alarm alerts are false—a serious problem for police departments.

Most local jurisdictions have ordinances to minimize false alarms by prohibiting alarm systems from directly contacting the police. Instead, the system must notify a third party, usually at a central monitoring station, which is supposed to verify the emergency before calling the police.

In addition, most police departments fine homeowners for excessive false alarms. Although fines are seldom assessed for the first two or three mishaps in a calendar year, most police departments begin issuing fines for each subsequent occurrence—and increase the amount for each additional false alarm.


An alarm system consists of five main parts: sensors, control panel (the brains of the system), inputs that deactivate the system and adjust control-panel settings, alert mechanism, and a means of connecting components.


There are dozens of sensor types. Some detect the opening of doors and windows, some detect broken glass, and others detect an intruder’s body heat and motion.

Magnetic contacts are the most common type of sensor. A pair of magnetic contacts is installed with one contact on a door or window and the other on the adjacent frame. Contacts are separated when a door or window is opened, sending a message to the control panel, which in turn triggers an alarm. With a third contact, magnetic contacts can be placed on sash and horizontal slider windows so that the windows can be left in either of two positions—closed or partially open—without setting off the alarm. A false alert can occur if doors or windows are opened by family members while the alarm is on, or if heavy winds rattle a loose-fitting window. These sensors provide no protection if an intruder breaks the glass and crawls through.

Glass breakage sensing devices trigger an alert when they detect the sound of breaking glass. A broken wine glass or bottle may trigger a false alarm. Many installers consider these devices unreliable; others consider them useful.

Wired window screens are fiberglass screens with fine metal wires woven within. An alarm sounds when the screen is broken. Except when accidentally broken, these screens seldom trigger false alarms. Wired screens are the most practical way to place an alarm on windows that are often left open.

There are two kinds of motion detectors: passive infrared and dual technology.

Passive infrared motion detectors are equipped with an “eye” that detects moving heat differentials within their field of vision. They are normally turned on when the homeowner is not in the house or asleep. Midnight snackers or unwary houseguests can cause false alarms. Other changes in room environment also can cause false alarms—for example, a dramatic shift in light from a blown curtain or a bug crawling on the lens of the device.

A dual-technology motion detector combines passive infrared detection with microwave technology. In addition to “looking” for moving heat differentials, this type of motion detector bounces sound waves off everything in a room. When something interrupts the consistency of the sound waves returning to the device, the detector checks the passive infrared detection. Unless both technologies are tripped, the alarm will not sound, enabling the dual-technology detector to verify a change in environment and be slightly less prone to false alarms.

Some motion detectors can be specially set to accommodate pets, creating a “pet alley.” Basically, the eye of the detector is aimed at a level above the pet’s normal path so that it will not detect the pet’s movement. While convenient in theory, pet alleys are far from foolproof because pets don’t always stay low. Cats climb on things, and dogs jump up and interfere with the detector’s line of sight.

Control Panel

The control panel receives and processes signals from sensors, and activates one or more alarm mechanisms. It also communicates with various inputs (keypads, remotes, smartphone software, etc.) to turn the system on and off and make adjustments. Whenever a sensor detects an opened door or window, or broken glass, or movement of a warm body, the control panel is alerted. If someone inputs the correct code or uses an appropriate key fob or remote 10 to 30 seconds before or after the alert, the system presumes it was caused by authorized occupants of the house. Otherwise, it activates an audible alarm and notifies a central monitoring station.

Control panels usually have from six to 32 zones. A single sensor or multiple sensors can be “grouped” into individually identified zones, allowing the control panel to indicate more precisely the location of a tripped sensor. The fewer sensors in a zone, the easier it is to pinpoint what caused an alarm. In a burglary, you seldom need to know more than which room an intruder has entered, but in order to identify a malfunctioning sensor it is preferable to put each sensor on a separate zone.

The panel should have a self-recharging backup battery that allows the system to continue operating during power failures.

Panels are available with various other features, including fire detectors, flood detectors, and medical alerts. And some trigger different-sounding alarms for each type of problem.

Some panels can be set so that frequently used windows will not trigger an alarm if they are closed quickly upon opening, or if they are opened so that they align a third set of contacts. It’s a convenient feature because you don’t have to enter a code or hunt down a remote or smartphone every time you open these windows.

Most panels can produce a pre-alarm warning, a moderate-level sound indicating that an alert has been received; unless canceled within 15 or 30 seconds, the full alarm will be triggered. This gives homeowners a chance to cancel alerts caused by their own mistakes—a good way to prevent false alarms. The pre-alarm warning should be audible throughout the house and outside all doors. A buzzer in only the control panel is insufficient.

The pre-alarm feature also notifies intruders—who usually flee but may instead try to destroy the control panel or prevent it from sending a signal. Good practice places the control panel in a securely attached, locked metal box with no exposed wires. Alternatively, install it in a locked closet or a difficult-to-find place.

Many control units are now equipped with self-silencers. After a siren has sounded for five to 15 minutes, it automatically turns off. Your neighbors will love this feature, and local ordinances may demand it. Some units automatically re-arm the system after the self-silencing; if an intruder leaves a window open or a malfunctioning sensor causes an alert, the siren will cycle on again until the alarm system is reset. The best compromise often is for the system to automatically silence the siren, turn off the triggered zone, indicate that the triggered zone has been turned off on the keypad, and leave the other zones active.

Keypads and Other Inputs

Various inputs—keypads, key fobs, touchscreens, software on your smartphone, remotes—can be used to control your alarm system.

If your system uses keypads or key fobs, devices should be installed near all frequently used exterior doors so occupants can enter the code or use their key fobs each time they enter or exit. A big benefit of smartphone home security software is that it easily lets you arm the alarm before going to sleep at night and disarm it in the morning. In addition, if an alert sounds at night you’ll know which sensors triggered it without going elsewhere in the house.

Some systems have inputs that are easier to operate than others. Ask company representatives to explain how their systems are controlled and exactly what you will need to do to set the alarm, cancel it, reset it, and get information on alerts for specific zones.

Most systems allow homeowners to manually trigger a burglary, fire, or medical alert by hitting a “panic button.” Some control panels can also receive signals from ill or elderly occupants wearing small wireless medical alert pendants.

Alert Mechanisms

The most popular alert mechanisms are sirens or horns mounted inside and outside the house. Outdoor devices more likely to attract the attention of your neighbors, passersby, and the police are also loud enough to be heard within the house. But if your false alarms are more than rare, an external siren will antagonize your neighbors.

Systems that include fire, flood, or medical alert sensors should have multi-tone sirens that distinguish between various kinds of emergencies. Since it is easy to forget which noise indicates which type of alert, some systems feature enunciators that alternate a loud blaring noise with a verbal description of the emergency.

Although central monitoring stations will inform the police of your address, some homes do not have street numbers prominently displayed. Because the sound of an external siren often echoes, making it difficult to know which house is emitting the alarm, many experts suggest also mounting a strobe light on the front of your home.


The components of an alarm system can be “hardwired” to the control panel with low-voltage wires or wirelessly communicate via small battery-powered radio transmitters and receivers.

Wiring for hardwired components may be fully hidden, partially hidden, or fully exposed. Fully hidden wiring is common practice but expensive to install in houses without unfinished basements or attics, and impossible to install in houses with concrete slab foundations and solid masonry walls. Have representatives of companies that propose to install hardwired components show you exactly where the wires for each component will run, and specify who will be responsible for the cost of any carpentry, plaster work, or painting needed to repair the damage incurred by the installation process.

Some wireless components are “supervised,” which means that each transmitter periodically sends a test signal to the control panel; if it fails to send the signal, the homeowner or central monitoring station is notified of the malfunction. Otherwise, you have to test the transmitters by going around and activating them, a chore few homeowners perform as often as advised.

Both types of components wind up costing about the same: Wireless components initially cost more, but hardwired components have higher installation labor costs.

While ease of installation is a big advantage of wireless components, the main disadvantage is that they are slightly less reliable than hardwired systems. There’s also the expense and bother of periodically replacing batteries, although batteries for most components should last several years.


Most control panels communicate with monitoring stations by transmitting signals via landline or cell signals. Although burglars usually flee soon after sirens go off—and well before police arrive—the police will come by to close any open windows and doors, and the monitoring station will notify the homeowner. Central station monitoring provides extra protection against determined intruders who defeat the siren, locate and destroy the control panel, or simply disregard the alarm.

Different jurisdictions have different policies for what central monitoring stations are supposed to do when alerted about potential intrusions. Before you sign a contract for monitoring, check out the current rules with the monitoring company and local police. The most common policy is that when an alarm is triggered the monitoring company calls prearranged phone numbers to make sure it isn’t a false alarm before notifying the police. If it is told it’s a false alarm, the person who answers must provide the correct password.

Test the service’s response by deliberately triggering an alarm and seeing how long it takes the station to call you. Some control panels have a “test mode” in which a siren emits a low-level noise or silences it so it won’t disturb your neighbors.

But just as the alarm industry is upgrading its technology, so are professional burglars improving their bags of tricks. If you live in an affluent neighborhood, or are known to have valuable possessions, ask alarm installers about the precautions you can take to protect central station communication.

Also consider enhancing your system with video monitoring. Set up cameras to either record or transmit to a central monitoring station a video of activity around the outside and inside of your home. Systems can be set up either to start recording or transmitting only when some other sensor has been triggered or on a continuing basis. If the video is being transmitted to a central monitoring station on a continuing basis, the station will not ordinarily monitor the signal unless a sensor activates an alarm notification.

The large national alarm companies operate their own central stations. Some have stations in each major metropolitan area, while others have a single station. Large independents may also operate their own stations, but most of the smaller independents contract with a station for this service.

Before contracting with a monitoring service, make sure the communications will work. And if your phone service is set up to reject unidentified callers, make sure your monitoring service can get through to verify an alarm.

Standards for Alarms

Underwriters Laboratories (UL) “lists” equipment that meets specified standards. Equipment UL-listed for safety means that it has been tested and proven not to cause harm or injury when used in the appropriate manner. Equipment also can be UL-listed for a specific purpose—for example, alarm equipment might be UL-listed for “intrusion detection.”

Because new and more technologically advanced alarm equipment is constantly coming onto the market, not all quality products will be UL-listed. It takes time to test some of the newer devices. While purchasing products with a UL-listing is desirable, it is not essential. It is better to select an alarm installer with a track record of satisfied customers than one using UL-listed equipment.

If an alarm system uses wireless sensors, their transmitters must, by law, be approved by the Federal Communications Commission (FCC).

UL also certifies alarm installations in individual homes based on specified standards. The certificate for “Basic Systems” requires contacts only on external doors and one motion detector. Since the motion detector usually is turned off when the house is occupied during the day, easily accessible windows are left vulnerable during those hours. The certificate for “Extended Systems” requires extensive protection. Because UL certification involves random inspection of installations, it is expensive for installers and few participate. And even among those that do participate, not all their installations are designed to meet the standards.

If you use an established installer with high customer satisfaction ratings, you probably don’t need to worry about UL certification. But if your house is a high-profile target for intruders, Extended Systems certificates provide extra assurance of adequate protection. If you want this assurance, inform installers when you call them, and make sure the contract specifies that the installation will be awarded a UL certificate for Extended Systems. You will probably pay a premium for such an installation.

UL also certifies central security stations that monitor alarms, with UL standards for the building, equipment, and staffing, and inspections to ascertain continued compliance. A facility can be certified as a “Central Station Burglar Alarm” (CPVX), “Central Station Fire Alarm—Full Service” (UUFX), or “Central Station—Monitoring” (CVSU). There are only a few such facilities in this area. Again, while we would prefer UL certification, we would still do business with a station that has generated high customer satisfaction even if it is not certified.