Universal Security Instruments Hardwired Ionization Smoke and Fire Alarm with Battery Backup, Model MI106 Dual ionization-sensing chamber responds quickly to fast-flaming fires Interconnectable with all USI-brand 120V alarms using existing wiring Patented Quick Find alarm origination easily identifies the first alarm to sound in interconnected systems Ambient condition compensation adjusts sensitivity based on temperature and humidity, reducing nuisance alarms Comes with a ten-year limited warranty