Ionization sensor technology senses invisible fire particles, while a electrochemical sensor detects CO gas Smoke alarm operates on a 120V wired power source with a 10-year sealed lithium battery backup An 85-decibel alarm sounds & a red LED indicates the smoke detector is sensing smoke or fire Test-Hush button makes it easy to test the smoke detector and silence false alarms that occur from cooking or shower steam Interconnection capability: allows you to connect up to 24 Kidde smoke, heat, or...