So-called "self-resetting" fuses use a thermoplastic conductive element known as a Polymeric Positive Temperature Coefficient (or PPTC) thermistor that impedes the circuit during an overcurrent condition (through increasing the device resistance). The PPTC thermistor is self-resetting in that when the overcurrent condition is removed, the device will revert back to low resistance, allowing the circuit to operate normally again. These devices are often used in aerospace/nuclear applications where replacement is difficult.