Understanding Wireless Home Security Alarm Systems

Home Security System Configurations

This article focuses on how you may want to tailor your home security system based on lifestyle and cost. There are three main home security system (alarm) configurations to consider:

  • Perimeter Only
  • Perimeter with Backup (motion and/or Glassbreak)
  • Interior Only

Perimeter Only Home Security Configuration

A “Perimeter Only” system is just that – only the perimeter entry points to your home are protected.  Every door and window is protected by magnetic contact intrusion sensors and can be wired, wireless or a combination of both.  Generally all openings within easy reach will be protected.  This certainly means the ground floor(s) plus any basement windows or doors as well as selected windows on the second floor.  A good rule of thumb for upper story openings is that if there is a roof overhang, etc. that an intruder can be boosted by a helper then that opening should also be protected.  If the bad guy needs a ladder to reach the window/door and goes that route then you have another problem all together.  More on that later.

Perimeter with Backup Home Security Configuration

“Perimeter with Backup” is doing all of the perimeter openings as above but also including some backup intrusion detection devices.  Typically this would be Passive Infrared (PIR) motion detectors but could also include audio Glassbreak sensors. The issue being addressed is:

  • What if someone breaks the glass on my window and crawls through without actually opening the window?.  

This is a valid concern.  While FBI statistics show the vast majority of break-ins occur at doors its still possible to bypass your perimeter protection (magnetic contact) by simply not opening the window.  Of course this means the intruder now needs to crawl over jagged glass and creates a more visible sign that something is wrong at your home.  The reason burglars come through doors is its relatively easy with fast entry – and more importantly fast exit.  

Many homeowners have invested in expensive keyed (two-sided) deadbolts which unfortunately are installed on wood frame doors.  A simple crowbar held under a coat and then just a little pressure right at your front door splinters the door right open. It’s extremely hard for neighbors to see that anything is wrong.  

Deadbolt with key

One other thought I’ll mention that you need to consider – dead bolts.  I hate deadbolts for two reasons:

They create a dangerous safety hazard at night in the event of fire (do you keep a key in your pajamas?)

If you, your wife, or children come home and “surprise” an unwelcome visitor you trap them inside with you.  Better for all to allow them a ready escape.


Passive Infrared (PIR) Motion Detectors As Backup Protection

How motions detectors can be used as interior protectionAn interior motion detector is used to “backup” the magnetic contacts on the doors and windows.  PIR motion detectors can sense a moving heat source (such as a human body) within a room.  The range of these sensors vary but most are rated to detect intruders 35 to 50 feet from the sensor.  It must be line of site with no blockage such as glass in between the protection area and the motion sensor.  PIRs do not detect objects moving beyond your windows or see through walls.  Security manufacturers offer many Pet Immune models that can also accommodate pets such as dogs or cats.  While they do work pretty well they accomplish this by reducing the detection sensitivity of the unit somewhat.  My professional recommendation over the years has always been to only use motion detectors in areas without pets.  For instance if you lock your dog in your bedroom at night then motion detectors on the first floor are fine.  With the introduction of better Pet Immune models I’m now rethinking this advice.  

Glassbreak Detectors Used As Backup Protection

An alternative to motion detectors (especially with pets) is to use audio Glassbreak sensors.  These devices “listen” for the sound of breaking glass.  Simply just jingling your car keys will not trick these microprocessor driven devices.  They look for specific frequencies and impulse signature before tripping an alarm.  A single Glassbreak sensor can in most cases cover an entire room of windows such as a Family Room even with the drapes closed. Closed drapes is actually part of the pre-installation testing for proper positioning/mounting of the device  


Interior Only Home Security Configuration

An “Interior Only” system is the least expensive of the three configurations by far, yet still provides a reasonable level of protection.  In this configuration you protect all doors on the ground floor(s) and use PIR motion detectors to cover the exposed window entries.  If you are only going to set (arm) the security system when you go to bed or when no one is home then this system configuration may be adequate.  However if you will be setting the security system at any time of the day or night (such as 7:30pm) then obviously you can not arm the motion sensors. Rooms such as your Family Room or Kitchen can not have an active motion detector while you are roaming the house.  

The Interior Only Configuration creates a serious “hole” in your defenses – no protection from entry through a window.  Glassbreak sensors can be activated while in the area unless you plan to break some glass panes within earshot of the sensors!  Glassbreak sensors can and should be active 24×7.  There is little reason not to have them enabled all the time just as your smoke detectors would be.

One other point that is important to consider:  

You may be detecting an intruder that is now “inside” your home.  Better to detect an intruder with his feet on your grass (while opening a protected window) than on your Living Room rug via an active motion detector.

Whether an Interior Only system is adequate is a personal use question as well as project budget.  Scare tactics designed to get you to buy for more protection is used all the time by security dealers. Remember the vast majority of break-ins occur through doors because of ease and quick entry/exit.  If you just need to be secure at night while sleeping or out of the house completely and Interior Only configuration may make the most sense.  You can always add protection at a later date as your need and budget allows.


Wired versus Wireless Protection

Wired protection devices such as magnetic contacts, motion sensors, glassbreak sensors, smoke detectors come in both wired and wireless versions.  There are two distinguishing factors to help judge which is best for your application:

  • Wired devices are the least expensive (cheaper by far)
  • Wireless devices are easier to install (faster by far)

Here is an easy rule of thumb for windows and doors:  


For a wired installation figure a window/door will cost $10 for a magnetic contact and wire plus about an hour of labor.  This labor includes drilling the window sill and sash, fishing the wire to the basement, and pulling a line back to the control panel.  It’s not really hard once you do a couple but it is time consuming.  


For wireless installation figure about $29-39 per opening plus ten minutes of labor.  The labor consists of pressing an adhesive backed transmitter on the window/door plus pressing the magnetic to the window or door frame.  

There is programming time involved too but it’s about the same for wired and wireless.  You may want to contrast the DIY cost with typical dealer pricing of $75 per opening, wired or wireless.  

If you are not comfortable fishing wire then wireless devices are certainly for you.  Remember that time is money so this needs to be factored in to your cost budget.

You may also want to consider a hybrid system – both wired and wireless devices.  Doors and windows over an unfinished basement for instance can easily be wired.  The same goes for garage openings where hiding wires may not be an issue.  On the other hand second floor windows or windows in a room over a concrete slab are excellent candidates for wireless transmitters.  Most wireless controls are wireless device only, or may have a single zone for wired devices.  Wired control panels such as Honeywell’s Vista series come with just that, wired zones.  However you can add a wireless receivers to these wired panels getting the best of both worlds. 

Next Up – Home Security System Devices


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