Fulfillment by Amazon (FBA) is a service we offer sellers that lets them store their products in Amazon's fulfillment centers, and we directly pack, ship, and provide customer service for these products. Something we hope you'll especially enjoy: FBA items qualify for FREE Shipping and Amazon Prime.If you're a seller, Fulfillment by Amazon can help you grow your business. Learn more about the program. The First Alert SA511CN2-3ST Interconnected Wireless Smoke Alarm with Voice Location features an 85-decibel siren and voice alarm that tells you where the danger is located. A photoelectric sensor detects smoke while minimizing false alarms from cooking or shower steam. Interconnected smoke detectors in different locations are designed to work together, with one alarm triggering the other alarm during a fire, helping to provide the earliest warning for your family. In the event of a fire every second counts. If a fire were to begin in your basement and the alarm there sounded, you may not hear it right away if you're sound asleep two floors up. With traditional battery-operated alarms, you lose valuable time waiting for the smoke to rise to another alarm, on another level, before the alarm on your floor sounds. But with First Alert ONELINK alarms, if one detects danger, they all sound. This can alert you sooner, and it increases your chances of getting out safely. Until now, alarms that could signal each other were only available in homes with hardwired alarms requiring installation from an electrician. But First Alert ONELINK alarms communicate without wires. ONE Link-with Voice Location Smoke alarm is programmable with up to 11 locations in your home - when alarm sounds it will tell you the location of the smoke. The wireless feature allows multiple alarms to talk to each other - when one alarm sounds, they all sound. The wireless network operates on 914 MHZ 3 channels and will not interfere with other electronics. The ONELINK smoke alarms uses photoelectric sensing technology which is environmentally friendlier and which reduces nuisance alarms, making it ideal for cooking areas. It is also great for sensing slow smoldering fires quickly. A low battery signal alerts you to replace the battery. The test/silence button both silences a non-threatening alarm or low battery warning and allows you to test the unit's functionality. The AA batteries are easy to install in the convenient pullout battery drawer. Two AA batteries included.