What is an essential characteristic of a hard-wired smoke detector?

A hard-wired smoke detector receives continuous power from the electrical system, which is a fundamental aspect of its design. Unlike battery-operated detectors that rely on batteries, a hard-wired unit is connected directly to the home's electrical wiring, ensuring that it is always powered as long as the electrical system is functioning properly. This continuous power supply enhances reliability, as homeowners do not need to worry about changing batteries regularly, which can lead to failure in detecting smoke if the battery is dead or removed.

This characteristic is particularly important in ensuring the smoke detector is always operational, especially during power outages or emergencies, provided that an electrical backup system is in place. This consistent power source allows for the smoke detector to function effectively, providing an essential safety feature in residential spaces. In contrast, options that suggest mobility or reliance on battery power would not apply, as hard-wired detectors are designed for fixed installations and depend entirely on the home's electrical grid for operation.