These Philips Battery-Operated Window and Door Alarms provide a simple-to-use cost-effective security solution to protect you and your family. Thanks to reliable magnetic sensors and 120-decibel alarms a would-be intruder will think twice about entering your home. This set of four user-friendly alarms will provide you with the extra coverage you need. You can also choose between alarm or chime modes with the flip of a switch. When installed and armed the alarm will activate if the window or door is opened alerting you and deterring unwanted visitors. The simple wire-free design of these alarms are perfect for homes apartments dorm rooms and offices alike. Use the included double-sided mounting tape to attach them to your window or door of choice within minutes ? each alarm is powered by four LR44 button batteries (included). Experience great peace of mind by adding a dependable layer of security to your home with these Philips Battery-Operated Window and Door Alarms!