The most common ways that burglars gain entry to a home is through the front door and back doors and then followed by the ground floor windows. They do prefer them to be open but will force them open using whatever means they have. This is why having entry sensors as part of your home security system are very important in detecting a break in. They provide that first level of detection.

Once the sensor detects they are being opened it will send a signal instantly to the control panel either by wire or wirelessly that this is happening. Depending on the system and how it is configured the control panel will contact those monitoring the system (monitored or unmonitored/self- monitored) and sound the alarm. For more on how home alarms systems work see my post here.

There are 3 different types of sensors used to detect that a door or window is being opened by an unauthorized person.

Door and window sensors or contacts. These are in the most common use and come in 2 parts – with one part being a magnet and the other piece being a sensor (known as proximity sensors). When the door or window is closed the 2 pieces are close enough together that there is a circuit and this indicates it is closed. When they are moved apart, the circuit is open and the sensor has been tripped and a signal is sent to the control panel. The sensor piece normally signals the door or window is opened when they are opened by more than a half inch apart ( but it differs by system).

There are systems that just use these contacts as the sole way they detect a break in. This can be a cost effective way to provide some security. The GE Personal Security Alarm Kit uses this method and sounds a 120 decibel alarm when the door or window is opened. It doesn’t have a way to remotely notify you or a monitoring company that the door/window has opened.

Vibration sensors.
These sensors detect when there is a vibration on a door or window such as when they are being kicked or forced opened. They are sensitive enough to determine whether it is just a ball hitting the door, a knock or something more sinister such as when a door or window is struck to break or force it open. They can be unreliable as they often give you false alarms from things they are supposed to be ignoring. These are not usually are core part of a home security kit but are more often something that can be bought as an extra.

There is a new system coming out – the Korner Home Security System designed for apartment security which relies solely on vibration technology for detecting the forcing and opening of a door or window. It is designed as an affordable method to provide people home security for those living in an apartment. It is a small triangle piece that sits on the corner of the door or window and when it detects an event it sends a notification to your smartphone via the internet. It doesn’t work with any other devices at this stage.

Glass break sensors. A problem with door and window contacts is that they can be bypassed by someone breaking the glass in the door or window. Unlike vibration and door/window contacts a glass break sensor can cover more than one window or door at a time. They are set to detect the sound of glass breaking and then trigger an alert. They are not mounted on the door or window but on a wall in the room so they can easily cover all the windows in the room

They do tend to be more expensive than window/door sensors but they can cover more at a time however, if a window is not smashed they won’t detect a forced entry.

Shops and other businesses use a beam of light to detect people coming through an open door to notify them. These could be used in a home security system in theory but aren’t in common use and I’ve not come across them in wireless DIY home security systems. I’ve mentioned them for completeness, but won’t go into their use.

After a burglar has made entry into the home the next level of security detection is the motion sensor which detects movement in an area they’ve been positioned to detect movement. They commonly use heat detection through passive infra red sensors.
It is a secondary level of detection as it happens after the criminal is already in your home, but provides a way to confirm a break in or detect the break in if the criminal has somehow bypassed the entry sensors.

Some systems such as the Canary Home Security System, again designed for apartments, just rely on the motion sensor for detection – it does make it easier to set up and control but does mean that an unauthorized person is already in your home or apartment before the alarm is sounded.

It is recommended when setting up an alarm system that you cover at least your entry points on the ground floor with door/window contacts to get notification and the alarm sounded as early as possible. Many criminals will leave when they hear the siren as they do not like noise and don’t want the attention that it may bring. If they do carry on they will often not spend as long in your home and won’t steal as much as they would have if there wasn’t an alarm sounding.

Entry sensors are simple devices that provide a good way to detect and start the notification and siren sounding process to deter burglars from carrying out their crime. They aren’t foolproof and can be got around and that is why it is important to include them as part of an overall system that includes motion sensors and/or surveillance cameras to be able to protect your family, home and valuables when you aren’t around.

Filed under: Buying Advice

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