One-pole supplementary protectors are used in a single circuit to interrupt currents in the event of an overload. They're UL1077 listed for use as extra protection from electrical damage for devices that already have branch circuit protection or where branch circuit protection isn't required. These protectors follow trip curves to determine when they will interrupt the current. If the current exceeds a device's rating up to a certain factor, the circuit breaker will have a delayed trip to prevent nuisance tripping. If the current exceeds the device's rating at or above that factor, it will immediately trip. They're mounted on standard 35mm DIN rail in applications like luminaires, appliances, control circuits, and control power transformers.