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 1cm Open state: When the distance between the host and the magnetic strip is more than 1cm, 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 Can adjust volume) Specification: Size: 6.5x3.4x1.65cm 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 1-3cm measuring deviation due to manual measurement. ( 1 inch = 2.54 cm )