Heilind Electronics, Inc. Datasheets for Resettable PTCs

Resettable (polymeric or positive temperature coefficient -  PTC) fuses are unlike traditional fuses that have to be replaced after a fault condition, this may not be necessary when using resettable fuses. The internal resistance of the component increases in response to an overcurrent or a short-circuit condition, limiting subsequent disturbances. After the fault condition is removed, the device cools and the internal resistance drops to nearly its initial value, permitting normal equipment operation to resume.
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