Eaton Bussmann series offers PTC devices suited for protecting applications sensitive to high ambient operating temperatures or subject to frequent overcurrent conditions. PTCs operate as a positive temperature coefficient device. High temperatures and excessive current will cause the device resistance to increase until it limits the unsafe current level.

Upon reaching the design temperature/current limit, the PTC will effectively "open" the circuit to provide protection from the overcurrent or elevated ambient temperature condition. Once the fault is removed or the ambient temperature cools, the PTC will automatically "reset" and conduct safe current levels again, allowing current to flow through the circuit.