Small Size Alarm: Compact design, smaller than most door window alarms. DIY installation, just Peel & Stick. It is easy to mount this alarm on any type of doors and windows, swing doors, rolling doors, sliding doors, etc. Loud Burglar Alarm: In constant alarm mode, once triggered, the continuous alarm will be a great deterrent to thieves and intruders. In doorbell mode, a loud sound will be an effective and timely alert when your children or pets sneak out of the house. 4 Working Modes: General Alarm, Constant Alarm, Door Close Alert, Doorbell Mode. Simply flip the side switch up and down to set the modes. Each mode corresponds to a different tone. Please refer to the product image for details. Ideal for: Not only suitable for all kinds of doors and windows, but also for drawers, filing cabinets, safes, garage, RV, office, warehouse, store, etc. Low Battery Indication: Powered by 3 LR44 batteries. Low battery consumption and long standby time. It will sound "Du Du" every half hour