Door Alarm : What is it?
Door alarms prevent intruders from breaking into a house by emitting loud sounds to alert homeowners. They use a number of detection systems, such as infrared and electric current, to detect suspicious motions or the presence of a person outside an entrance. Some door alarms have an emergency call feature that automatically calls local law enforcement when an intrusion attempt is detected. When used in business establishments, they may include special sensors that set off the alarm when unpaid merchandise is passed through the door. Door alarms may also be installed over other entryways, such as windows.
Kinds of Door Alarms include the following:
- Chain alarms are connected to standard door chains and are activated from indoors.
- The chain track is pressure-sensitive, which causes it to trigger the alarm when the door is kicked in.
- Since they cannot be activated from outside, they cannot be used to guard empty houses.
Magnetic contact alarms
- These door alarms consist of a magnetic contact switch attached to the door frame, and a siren contained in a small oblong box.
- The contact is broken when the door is opened, setting off the alarm.
- They can be activated from outside, allowing them to protect a house when the residents are away.
- They can also be installed on windows, safes, cupboards, and gates.
Glass break detectors
- Glass break detectors have sound-sensitive alarms that are triggered by the sound of breaking glass.
- They can only be used in glass doors and windows, and will only sound the alarm after the intruder has broken in.
Passive infrared detectors
- These detectors use infrared waves to detect changes in room temperature that indicate a person’s body heat.
- They are used as personal alarms installed in bedrooms to alert residents of intruders elsewhere in the house.
|Wired vs wireless: Choose a wireless door alarm if you are installing only on one entrance. If you are placing several units with personal alarms, choose a wired model to ensure constant communication between the personal alarm and the door unit. For wireless models, make sure they can run on both AC power and batteries, so that you have a backup source when AC power fails.|
Panic switches: Choose a door alarm with a panic switch to alert authorities when you confirm a break-in. These are more reliable than emergency call alarms because they work without using the phone connection.
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