October 2021

Alarm systems can be comprised of a wide variety of devices that work together to protect your domestic or commercial property. Door contacts are often requested or advised when designing and installing an intruder alarm system. Below, we describe what contacts are and how they are a vital part of your home’s security ecosystem.

The primary use of contacts is to be fitted to doors that lead into the property such as a front or back door. According to ONS statistics, doors are used as access in 70% of domestic burglaries, with window access making up the other 30%. Since doors are the most used method of breaking into a property, it is often these devices that are triggered first. They can also be fitted to windows of a building so may also be referred to as window contacts. Use of these on the interior of the home can also be considered for those wanting to keep specific items away from others such as firearms or an alcohol cabinet.

Door contacts are comprised of two parts – a sensor and a magnet. One part is fitted to the door, with other part fitted to the door frame. The two parts utilise a magnetic field to determine their proximity to one another. When together, an internal reed switch in the sensor is closed. When the door is opened the magnet separates from the sensor – opening the reed switch which sends a signal to the panel. This enables the alarm system to know if a door is open or closed and to act accordingly.

Different versions of door contacts exist. Surface mounted contacts can be mounted on the onside of the door. Flush mounted versions can be fitted within the inside edges of a door and the associated frame for a clean finish. Surface mounted contacts are usually easier to install as no drilling out is required. However, the type used depends on the design of the door and the material they are being fixed to.

Both wired and wireless versions of contacts are available which make them suitable for all systems in one way or another. Wireless door contacts communicate with the alarm panel using wireless radio frequency. This type gives certain flexibility as they can be removed and placed on a different door if required and are easy to install onto an existing system as long as the panel supports the use of wireless devices. As they are unable to receive power via a cable, wireless contacts use batteries and so require routine battery changes to ensure they are working continuously.

Wired contacts use direct hardwired cabling to communicate. As such, ongoing maintenance can be less than wireless contacts. However, changing the location of an existing hardwired contact or incorporating additional contacts is more complicated, with new cabling required.

Unlike PIRs, door contacts require the two parts to separate to cause an activation and are unable to detect motion within the property. They can be ideal if you are on a budget as covering the external doors rather than each room can reduce the number of devices required. It is important to note though that each house is unique and exploring the use of PIRs in conjunction with door contacts is advised in most cases. Interested in how PIRs work? Click here to read about them.

Need more advice or want us to design and install a system for you? Contact us on the telephone number above, the enquiry form below, or send us an email at [email protected].

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