NB-IoT door and window alarm is mainly used for anti-theft and gate access control. Working principle: The distance between the alarm host and the magnetic stripe is more than 15mm, the alarm will immediately sound an alarm and at the same time send an alarm message to the mobile phone. The mobile phone (mini-program / APP) can be armed and disarmed with one click, and the status of the door sensor switch can be checked in real time. Can be used indoors / outdoors.