4 in 1 Mode: This alarm with 4 modes. 1. Timing alarm (sounds "Di-Di-Di" from 0dB to 108dB if door stay open for 3/15/30/60s) 2. General alarm (alarm stop if door closed); 3. Constant alarm (constant alarm even closed door); 4. Door opening chime (sounds DingDong once the door is opened) Loud 108dB alarm: Door and window alarm helps effectively deter intruders/ thieves with a loud 108 dB alarm. You can easily set the suitable mode according to your needs. Easy to Install: Simple peel and stick installation, easy to install on most freezer/refrigerator or any door without any tools. package including 2 fridge alarms, 2 magnetic strips, double-sided sticker, user manual. The electronic instruction is on the eighth picture. Note on installation: be sure to close the alarm and the magnetic strip, the installation distance between them should not exceed 0, 78 inch. The 2 parts must be aligned by their alignment arrow. 2 AA batteries can stay for 2 years. (Batteries are not included) Widely Used: Magnetic Trigger Door Alarm Sensor Protecting Home Through Door Window Entrance and Suitable for Safe, Cabinet, Freezers , refrigerators, swimming pool sliding door, shop, office, apartment, hotel, etc.