Door magnet system is a safety alarm system, which is divided into door magnet and window magnet (the principle is the same and the shape is different). Door magnet / window magnet is not easy to see if you don't pay much attention. The so-called door magnet / window magnet is actually the abbreviation of door magnet switch and window magnet switch, which is composed of two parts: the smaller part is permanent magnet, and there is a permanent magnet inside to generate a constant magnetic field; the larger part is the main body of door magnet, which has a normally open dry reed tube inside. When the permanent magnet and the dry reed tube are close (less than 5mm), The door magnetic sensor is in the working waiting state. When the permanent magnet leaves the reed tube for a certain distance, it is in the normally open state.
The magnet and reed are installed in the door frame (window frame) and door leaf (window sash) respectively. They are basically embedded (also surface mounted), so people in the industry generally can't pay attention to these. You can open the household door and the external window, look at the top of the household door frame and the window frame of the external window, and you can see the circular and generally white components. In fact, this is the so-called door magnet and window magnet.