There are two main types of door and window contacts: surface, and recessed.
A recessed door or window contact works exactly as a surface contact, but the sensor and magnet are installed "inside" the frame and window or door. They are completely invisible, and less prone to tampering. Recessed contacts are used most often in office and residential settings.
The cost difference between surface and recessed contacts are minimal, and using recessed contacts is generally worth the few extra dollars.
A garage door contact is similar to a surface door contact in appearance, and work on the same principle. However, in this case the sensor portion usually installed onto the floor, while the magnetic portion is installed on the garage or roll up door itself. The sensor portion is encased in steel, which can withstand a vehicle driving over it on a regular basis.
Above: Standard Surface Contacts For Doors And Windows Are The Least Expensive.
Types Of Magnetic Alarm Contacts For Your Doors And Windows:
Above: A Standard
Garage Door Or "Roll Up" Door Contact, Popular For Industrial Installations.
Tip: Use standard magnetic contacts on any "sliding" windows in your home or business. For casement windows ("crank" style), use a standard or button glassbreak detector. Why? Because casement windows (when they are closed) are virtually impossible to open without breaking the glass, whether they are locked or not. And the burglar may just remove the glass, and enter your home or business without even opening the window!
Above:
Recessed Door And Window Contacts Are Virtually Invisible.
Door or window Surface contacts are easiest to install and cost the least. The sensor is placed onto the "surface" of the frame, and the magnetic contact onto the "surface" of the door or window itself with a strong adhesive backing. Surface contacts are usually used in commercial and industrial applications, but are also used in residential installations (i.e. laundry rooms, garage doors). They are not used as much in a residential setting purely for esthetic reasons.
Doors and windows can utilize magnetic contact sensors as a way of detecting when the door or window is opened. The sensor is housed or placed on the frame of the door or window, and the magnet is installed on the door or window itself. When the two lose contact with each other (by opening the window or door), the "circuit" is broken, and the signal is sent to the alarm panel.
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