4 in 1 mode: this alarm with 4 modes. 1. Time delay alarm (sounds 'Di-Di-Di' from 0dB to 108dB if door remains open for 3/15/30/60s) 2. General alarm (alarm silence if door closed); 3. Constant alarm (constant alarm even closed door); 4. Door opening chime (sounds DingDong once the door is opened) 108 dB loud alarm: Door and window alarm helps effectively deter intruders / thieves thanks to a loud alarm of 108 dB. 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 any hassle. tool. package including 2 refrigerator 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 pieces must be aligned by their alignment arrow. 2 AA batteries can last 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, store, office, apartment, hotel, etc. Number of pieces delivered: 2