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A home door alarm is designed to be placed on doors in homes to provide security by alerting the residents that the door is being opened. When a door with an activated alarm is touched, the alarm sounds at 110 or 120 decibels. That sound level is loud enough to be heard throughout most homes. There are many different types of home door alarms and the prices range from as little as $6 U.S. dollars (USD) to more than $100 USD. Many of the door alarms available today are wireless.
The keypad type of home door alarm is usually meant to be mounted on the wall near the door, and a code number activates and deactivates the alarm. Other kinds of home door alarms are portable and don't mount onto the wall. Some alarms hang directly on the door knob and emit a siren like noise if the door knob on the other side is touched. This type of home door alarm is made to take along when traveling, such as to use on a motel room door for extra security. Some hanging door alarms can also be carried as a personal alarm.
Doorstop home alarms look similar to an actual door stop device, as they are wedge-shaped and are placed with the narrow part under the bottom of a door. If the alarm is set when the door is opened from the outside, the alarm sound will be triggered. Another type of home door alarm is made specifically for home swimming pool gates so parents can be alerted if a child is near the water. There are also home door alarms created for use on sliding glass patio doors. Part of the alarm usually needs to be bolted to the frame, while the other part fits onto the door itself.
A home door alarm may be used not only to keep burglars out, but to keep people in the home for their own safety. For example, a small child may wake up before his or her parents and try to open a front or back door and go outside. If the parents have alarms set on the doors that they can hear and that will wake them, a dangerous situation may be prevented. This also may work in the case of Alzheimer's patients who often become disoriented and may try to wander out of a home in a confused state.