Alarm System Elements 2

Elements of an Alarm System Part 2

Door and Window Sensors—the Magnetic Contacts

A break in the magnetic contact trips the alarm when the door or window is opened. Some magnetic contacts are concealed within the frames of door or window frames. Others are small, plastic devices that mount on the surface of door and window frames. For entry doors, an entry/exit delay is programmed into the system to allow you time to enter and leave through specified doors without setting off the alarm.

Alarm Screens

Alarm screens replace the insect screens on windows that open. They are also almost identical to regular screens. When the screen is cut or removed from the window frame, the alarm will go off. Alarm screens are the most expensive type of window sensor, however, they protect the entire window space, even when the window is open!

Acoustic Glass Break Sensors

Determined thieves can get around door or window sensors by breaking out the glass and crawling though—without actually opening anything. Acoustic glass break sensors will detect this type of intrusion. It does so because the little electrical devices pick up the unique sound frequency of break glass.  One acoustic glass break sensor will cover all the windows in a single room. There are glass break sensors designed to mount on the window frame. These have a built-in magnetic contact to detect either the window being opened or the glass being broken.

Motion Sensors

The most common type of motion sensor is the PIR (Passive Infrared). This miniature electronic device is a low-cost, reliable unit that detects body heat and is in a corner of the room near the ceiling. Typically, PIRs should be placed so that no object that quickly changes temperature is within its field of view such as heater vents, wood stoves, fire places, and sun-heated windows. A PIR is the most effective at detecting a person walking across the room consequently, be sure to mount the sensor where it can pick up anyone trying to cross the sensor’s field.  If your pets have free run of your home, it is important that you choose a pet-immune motion sensor.

Portable Alarms

If you don’t like the idea of installing a full system, or don’t have a place to mount a motion sensor, try using a portable alarm. These battery-operated, self-contained units are motion sensor and alarm in one. They are an excellent choice for apartments or an added security measure while staying in a hotel room.