From the Manufacturer
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. The First Alert ONELINK SA501CN2-3ST Twin Pack of 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.