Understanding How Door Alarms Work

There are many different door alarms on the market today. I'll cover several of them so that you'll have a basic understanding of how door alarms work, starting with my favorite that door stop alarm. I like this unit because it protects in 2 ways. Being a door stop it also stops the door from being opened as well as sounding a siren when someone tries to break in. There is a pressure sensitive switch in the base that activates the alarm when the door is pushed against it. Another reason I like this unit is that it's portable and can be used anywhere.

Next let's talk about a unit that's not only a portable door alarm but also a window alarm as well. When looking into how door alarms work this warning device functions the way many of them do. It has an attachment with a sprung metal clip that you slide between the door and the jam (or the window and the sill). With the door (or window) closed the connection between the two pieces of metal are held in place completing an electrical circuit. If however the door (or window) is opened they spring apart, the connection (and the electrical circuit) is broken and the siren goes off. Really, understanding how door alarms work is not that difficult.

What you may think of when you think "door alarm" is 2 contacts, 1 mounted to the door, the other mounted to the frame, connected by wiring to a box or keypad, like you would get form ADT or any of the big alarm companies. This type works exactly the same way as the one in the last paragraph does. When the door is opened, and the contacts separate, the connection is broken which causes the alarm to go off. The only difference is it can't be moved.

PIR (Passive InfraRed) motion sensors are not door alarms per se, but let's look at them anyway. These sensors can be connected to a base unit either by wire or wireless transmitter. They operate by detecting variances between a persons body heat and the normal background temperature. Let's complete our understanding of how door alarms work by looking at an instant door alarm which can also be used as a personal alarm. This one works by creating an incomplete electrical circuit. It comes with a chain that is placed on any metal door knob. An electrical impulse is sent by the unit through the chain to the door knob that is not grounded until it is touched by someone. When anyone touches the door knob they become the ground, completing the electrical circuit, and the alarm is instantly triggered. The drawback is that it can't be used on a metal door (because it would become the ground).

About the authur: My name is Mark Strong and I live in Loveland Ohio with my lovely wife Patricia. We hope that everyone will benefit from the information and products we provide and have a safer, happier more secure life. www.affordablestungunplus.com/homeprotection.htm

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