Feature: Working principle of induction door magnetic: When someone illegally opens a door or window (the host is separated from the magnetic strip), the door magnetic alarm immediately emits a sharp alarm sound. Closed state: No alarm will sound when the distance between the host and the magnetic strip is within 1 cm. Open state: When the distance between the host and the magnetic strip is more than 1 cm, a loud alarm sound will be emitted. Five modes: - Door opening alarm, door closing stops - Ding-Ding doorbell mode - Door opening alarm for 30 seconds - DI DI DI mode - After 15 seconds of opening the door, the alarm will sound for 30 seconds before it ends (Short press to switch modes; Volume can be adjusted) Specification: Size: 6.5 x 3.4 x 1.65 cm Package Included: 1 x Alarm Note: 1. Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you! 2. Please allow 1-3 cm measuring deviation due to manual measurement. (1 inch = 2.54 cm)