When traditional fuses are being used for overcurrent protection it can only protect once then it must be replaced. The PTC resetable fuse is a new-type of overcurrent protection element which has two functions providing overcurrent protection and automatic reset. The overcurrent protection PTC element is serially connected to the circuit and under normal circumstances it provides a low resistance state and can ensure the normal working of the circuit. If a short circuit or unusually high current occurs, the PTC fuses cut in to reduce the voltage down to a trickle thus preventing damage and protecting the equipment. The PTC fuse will automatically reset once the fault in the overcurrent is removed. The PTC elements will automatically return to its low resistance state, which not only avoids maintenance or replacement but also avoids a continuously circulating switching state which can cause circuit damage.