The automatic sensor alarm will protect your home safety.When a thief or aggressor opens the door, this inductive door alarm will sound an alarm and help prevent the intrusion. The wireless door alarm will be activated when the magnetic sensor is separated. This doorbell can help you protect the safety of children at home as well as the elderly and dogs. It will remind you when they accidentally open the door or window. You can also use it in stores and offices where important documents and belongings are stored.The separation of the main unit and the magnet by more than one centimeter will trigger an alarm, up to 125 decibels, and it will never be a useless alarm. Safe power consumption guarantee, low consumption, can be maintained for 6 months in standby mode. Please note that the LED light of the main unit turns red to indicate that the battery needs to be replaced.There is no need to punch holes, just tear off the adhesive film on the back to stick on the edge of the fish door frame. You can also use it when you go out to stay in a hotel. Small and convenient.This product does not include batteries, you need to bring your own three LR44 batteries! ! ! ! ! !