Mz12a thermistor is a kind of protection element for automatic protection and recovery of abnormal temperature and current, commonly known as "self recovery fuse" and "ten thousand times fuse". Instead of the traditional fuse, it can be widely used in over-current overload protection of motors, transformers, electronic circuits, etc. The thermistor can reduce the residual current value by limiting the consumption of the whole circuit through the sudden change of its resistance value. In the traditional fuse circuit, it can not recover itself after the fuse is blown, while the PTC thermistor can recover its protection function after the fault is removed.