The very first burglar alarm systems installed by Edwin Holmes in the 1800s consisted of simple door contacts that would activate an alarm signal at the central station when the door was opened. These first door contacts were mechanical, with a strip of metal positioned so that when the door was opened it would open or close an electrical circuit.

The next evolution in door contacts was the development of the two-piece contact, where a magnet was installed on the moving part of a door, window, or other opening. When the door is closed, the magnet is within close proximity to the contact device, which today contains a sealed reed switch that typically is closed and completes a circuit when the magnet is nearby.

As alarm systems have become more sophisticated, the methods of attacking and defeating alarms have also evolved. One way a burglar can defeat a standard door contact is to place a large magnet near the contact location. The large magnet can keep the standard reed switch closed even as the door or protected opening is being opened by the intruder and the dealer-installed magnet is moved away from the contact. A piece of duct tape can hold the foreign magnet in place, and the burglar can enter without activating the door contact and tripping the alarm system. A more sophisticated burglar would use smaller magnets and surreptitiously glue or tape the magnets onto the contact while visiting the target location during business hours, which can defeat the contact’s function and prepare that door to be violated.

Customers such as banks, jewelry stores, and other locations where high-value items could be stolen are candidates for the use of balanced high-security contacts. In a balanced contact, there is an internal magnet installed within the contact portion, which works with the external magnet that is attached to the moving door of a safe or high-value storage door. The special reed switch within the contact will maintain a closed or secure position when the door or safe is closed, with the two magnets maintaining the proper magnetic force to keep the reed switch in the closed position. If a foreign magnetic force is introduced, the reed switch will open causing an alarm signal to activate.

Honeywell provides the 968XTP balanced contact set for use on high-value items such as safes

Security dealers should consider the use of balanced contact sets when protecting any clients’ storage areas that contain cash money, jewelry, artwork, bullion or other high-value items that are particularly attractive to professional thieves.

It is also important to have the contacts that are installed on these high-value storage units to be connected to unique zones on the control panel, with those zones programmed for either daytime chime or 24 hour burglar alarm sounding and reporting. The client should always be audibly notified when their safe or valuables storage room is opened, whether it is during business hours or otherwise.

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