4 in 1 mode: This alarm with 4 modes. 1. Time alarm (sound 'Di-Di-Di' from 0dB to 108dB if the door is open for 3/15/30/60s) 2. General alarm (alarm stop if the door is closed); 3. Constant alarm (constant alarm even closed door); 4. Door opening signal (sound DingDong when the door is opened) Loud 108dB alarm: Door and window alarms help effectively deter intruders/thieves with a loud 108dB alarm. You can easily set the appropriate mode according to your needs. Easy to install: Simple peel and stick installation, easy to install on most freezers/refrigerators or any door without tools. package including 2 cold alarms, 2 magnetic strips, double-sided sticker, user manual. Note about installation: be sure to close the alarm and the magnetic strip, the installation distance between them should not exceed 0.78 inches. The two parts must be aligned with their alignment arrow. 2 AA batteries can last for 2 years. (Batteries not included) Widely used: Magnetic trigger door alarm sensor that protects home through door window entry and suitable for safes, cabinets, freezers, refrigerators, sliding pool door, shop, office, apartment, hotel, etc.