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Alarm Systems

Burglar alarms have become standard equipment in stores and other businesses, and they’re becoming increasingly common in private homes as well. If you’ve ever shopped for a home security system, then you know there are a wide variety of options available. These systems range from do-it-yourself kits you can pick up for $10 to sophisticated whole-house security networks that must be installed by professionals. But, as it turns out, most alarm systems are actually built around the same basic design concepts. We’ll be looking into the basics behind home alarm systems in this post!

Other than the family dog, the most basic burglar alarm is a simple electric circuit built into an entry way. In any circuit, whether it’s powering a flashlight or a computer, electricity only flows when you give it a path between two points of opposite charge. To turn the electricity on or off, you open or close part of the circuit.

To open or close a flashlight circuit, you simply throw a switch. In a burglar alarm, the switch detects the act of intrusion — opening a door or window, for example. These sorts of alarms are divided into two categories:

  • In a closed-circuit system, the electric circuit is closed when the door is shut. This means that as long as the door is closed, electricity can flow from one end of the circuit to the other. But if somebody opens the door, the circuit is opened, and electricity can’t flow. This triggers an alarm.
  • In an open-circuit system, opening the door closes the circuit, so electricity begins to flow. In this system, the alarm is triggered when the circuit is completed.

There are a number of ways to build this sort of circuit into an entry way. Closed circuits are normally a better choice than open circuits because an intruder can deactivate the open circuit by simply cutting the connected wires.

A magnetic sensor in a closed circuit consists of a few simple components. For the most basic design, you need:

  • a battery powering a circuit
  • a spring-driven metal switch built into a door frame
  • a magnet embedded in the door, lined up with the switch
  • a separately-powered buzzer with a relay-driven switch.

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