Ltvystore Door Window Entry Alarm with Magnetic Sensor Pack of 2 Have doorbell and anti-theft function. Contains "chime" and alarm. Two kinds of voice can freely switch along with you. During the day can be welcome, In the evening can guard against theft Three 1.5V button cell batteries, INCLUDED Volume: 95 db Mounted using double-sided adhesive tape (included),Easy tool-free installation to window or door