What type of device requires a lineman to manually reset after a failure?

The correct choice is the automatic recloser, as it is a device designed to temporarily interrupt power in the event of a fault to allow for automatic restoration of service after a brief period. However, when numerous faults occur within a certain timeframe, the automatic recloser will lock out and require manual intervention from a lineman to reset it. This manual reset ensures that any persisting fault can be addressed safely and effectively.

In contrast, a fuse operates by melting its element during a fault condition, which permanently interrupts the circuit until it is replaced. A line sectionalizer is automatically reset after clearing a fault, and transformers typically do not have manual reset features related to fault conditions. Each of these devices has a unique function in managing electrical systems, but it’s the automatic recloser that necessitates a lineman's manual reset after multiple failures, highlighting its role in maintaining the balance between automation and safety within utility operations.