Alarm systems & Security systems have been in operation for more than hundreds of years. Though previously considered only the requirements of the only rich and famous but as the security threats have increased over the years more and more alarms have made their way into the normal family home.

Originally security systems and alarm systems used 'local' alarms, where, if someone intruded into your property, an alarm would sound there and then and alert everyone of the danger. Now more commonly, external monitoring centers are used to keep track of the home. If the alarm is triggered, not only will a 'local' alarm sound, but the remote monitoring center will also be alerted. This takes into account the possibility that the 'local' alarm will be ignored.

There is a wide variety of home security alarm systems to choose from, ranging from the cheapest DIY kit to far more sophisticated, professionally installed units.

Original home security alarm systems used a button to trigger the alarm. A button was fitted into a doorframe and was depressed when the door shut. If the door was opened and the button released, an alarm would sound. A substantially flawed method, as all the intruder needed to do to silence the alarm is close the door. Nowadays, Family dog aside, the most basic home security alarm is a simple electric circuit positioned in a doorway. Either the circuit is completed when the door is closed and so breaking the circuit will trigger the alarm, or the circuit is completed when the door is open and so completing the circuit will trigger the alarm. The only real practical difference between these is that in the latter circuit, the intruder could cut wires the thus silencing the alarm.

If an intruder does successfully make it inside, there are a number of different security alarm systems you could have in place. Using the similar notion of an electric circuit, pressure detectors can be created under a mat to detect intruders. If pressure is applied to the mate and the two sections of wire brought together, the circuit will be completed and an alarm sound. However, the most common is a motion detector, which detects temperature rise and/or mass movement, either of which will trigger the alarm.