Burglar Alarm technology has been around for over 100 years. While technology has advanced, some of the terminology still in use by dealers has not, and the use of door and window “contacts” is common to our industry.
A contact is a device that is typically attached to a door, window, or other entry point that would be opened or moved if someone tries to gain access during a burglary or “intrusion.” It is a very effective means for determining if a door is open, closed, or has moved.
The terminology refers to an early means of this detection. Most alarm technology involves establishing an electronic “circuit” by means of establishing a closed “loop,” and interrupting that loop. Back in the day a metal (usually brass) bar was placed on a door to complete the circuit by pressing against the similar parts connected to the wiring, thus completing the circuit. If the bar no longer made “contact” to complete the circuit then the zone was “open” and would cause an alarm or trouble condition so the alarm could not be “set.”
With the invention of the reed switch a magnet could be placed adjacent the switch to cause the reed to “close” and complete the circuit. If the door opened then the magnet moves away and can no longer keep the switch closed. This was a critical advancement because the brass bar could be damaged or corrode over time and cause troubles or false alarms.
There are now literally thousands of switches or contacts available to alarm industry professionals. One of the older companies, GRI (http://www.grisk.com/) located in Kimball, Nebraska supplies these Made in USA products world-wide.
Wireless technology uses this method for door and window protection without the use of physical wiring from the control panel to the door switch. These small devices have embedded serial numbers that help identify them to the control equipment, and are programmed into the control panel so they don’t get confused with other devices within range. They are also supervised so if one goes missing or is altered (damaged or the device is opened for battery replacement) the control panel notifies the alarm company.
Advancements in alarm technology help reduce false alarms and make alarm systems user friendly, and Security Professionals is part of that effort.