Small Size Alarm: Compact design, smaller than most door window alarms. DIY installation, just peel and stick. It is easy to mount this alarm on any type of doors and windows, swing doors, rolling doors, sliding doors, etc. Loud anti-theft alarm: In constant alarm mode, once triggered, the continuous alarm will be a great deterrent for thieves and intruders. In doorbell mode, a loud sound will be an effective and quick alert when your children or pets sneak out of the house. 4 working modes: general alarm, constant alarm, door closing 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 more details. Ideal for: Not only suitable for all types of doors and windows, but also for drawers, filing cabinets, safes, garage, camping -car, office, warehouse, store, etc. Low battery indication: Powered by 3 x LR44 batteries. Low battery consumption and long standby time. It will sound "Du Du" every half hour when the alarm is in low battery status. of principle: This alarm is an open window door alarm. The installation distance between the host and the magnetic bar should be less than 1cm. If the door or window is opened, the host and the magnetic bar will separate, the alarm will be triggered once the distance exceeds 1cm. Installation Instructions 1) Attach double-sided tape to the back of the alarm and the magnetic bar, then stick them separately on the 2 sides of the seam of the door or window. 2) Make sure the V-line of the 2 parts is aligned, make sure the distance between them should be less than 1cm. 4 working modes: 1) General alarm: the alarm sounds if the door is opened, the alarm sound stops if the door is closed. How to set: Flip the switch up. The quick sound is "Di-Di" 2) Constant alarm: Constant alarm even door closed. How to set: Flip the switch up, down, up. The prompt sound is "Di......" 3) Door close alert: sound "Di..Di..Di.." when the door is opened, it will s will stop when the door is opened. How to set: Flip the switch up, down, up, down, up. The quick sound is "Di-Di-Di" 4) Doorbell: ring "DingDong" if the door opens. How to set: Flip the switch up, down, up, down, up, down, up. The rapid sound is "DingDong" Alarm dimensions: 56x30x17 mm Magnetic bar dimensions: 35x10x10 mm Power supply for alarm: 3 LR44 batteries (included) What you will get: 2 Pack of alarms