If the current within an electrical circuit exceeds a specified value for a certain time, all the components connected can suffer damage. To prevent this happening, overcurrent protection is installed, which in the ideal case interrupt the power supply to the circuit before any damage results. Probably the most widely used such device is the fuse. These contain a fusible wire which melts when the current is excessive, thus breaking the circuit. In such cases the fuse must then be replaced. Self-resetting fuses have the characteristic that at high currents their intrinsic resistance increases. Once the current has returned to a normal level, the fuse is once again ready for use; it need not be replaced. Temperature-based fuses are activated when temperatures are excessive; they protect both people and machines against fire. The range offered by Bürklin Elektronik also includes fuses optimised for special fields of applications, such as photovoltaic systems or vehicles.