Protect your home and family with this USI Electric 5304 smoke and fire alarm! It's a hardwired ionization alarm, which means it connects directly to your home's electrical system for constant power, and it also has a battery backup in case the power goes out. This unit is sold as open box – it's brand new and fully functional but may have minor scratches and the original box might be worn. A fantastic way to get a high-quality alarm at a great price. Ionization sensors are great at detecting fast-flaming fires. Easy to install if you have existing wiring. Don't compromise on safety!