Shop for Electrical . The Kidde Hardwire Interconnect able Photoelectric Smoke Alarm with Battery Backup can act as a stand-alone unit or can be integrated into an existing electrical system. This unit sounds an early warning to alert you and your family of the presence of visible fire particles detected by the alarm's photoelectric sensor. Powered by 120 Volt AC, this alarm protects you, your home and the people you hold dear even during power outages, thanks to a 9-volt battery backup. A power harness facilitates an easy installation and a simple push of a button activates this alarm's test and hush features.