The innovative design of this Kidde SMOKE ALARM WITH SMART HUSH™ is unlike any other ... it automatically activates when attached to a mounting bracket! There are no pull tabs or switches - everything is totally automatic. And, it chirps when it reaches its 10-year alarm life, letting you know it's time for a new one. Plus, its self-sealed batteries mean 10 years of hassle-free operation and battery replacement costs. There's also a Smart Hush feature that temporarily silences nuisance alarms and a 4-mode flashing red LED indicator for Standby, Alarm, Hush and Memory Set.