What device in a series street light circuit maintains normal operation despite a bulb burn-out?

In a series street light circuit, the device that enables normal operation even after a bulb burns out is the film disc cutout. This device is designed specifically for such applications, where maintaining continuous circuit functionality is critical. The film disc cutout acts as a protective mechanism by detecting abnormal conditions such as an open circuit caused by a burned-out bulb or other faults. When this occurs, the cutout will automatically disconnect the faulty section while allowing the remaining lights in the series circuit to continue functioning.

This ability to isolate the problem ensures that street lighting remains operational, enhancing safety and visibility for motorists and pedestrians. Other devices listed, like fuses, relays, and breakers, have different functions; they may provide overcurrent protection or switching capabilities but do not perform the specific task of maintaining circuit operation in a series configuration when one component fails.