4 in 1 Mode: This alarm with 4 modes. 1. Timing alarm (sounds Di-Di-Di from 0dB to 108dB if the door remains open for 3/15/30/60s) 2. General alarm (alarm stop if door closed); 3. Constant alarm (constant alarm even door closed); 4. Door opening chime (sounds inchDingDonginch when door is opened) Loud 108dB alarm: Door and window alarm helps effectively deter intruders/thieves with a loud 108dB 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. Installation Note: 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, door slider for swimming pool, store, office, apartment, hotel, etc. Number of pieces delivered: 2