First Alert, 6 Pack, SC7010BV, Hardwired Talking Photoelectric Smoke & Carbon Monoxide Alarms, Features Photoelectric Smoke Sensors & Electrochemical Carbon Monoxide Sensors, Voice Alarm Not Only Alerts You Whether The Threat Is Smoke Or Carbon Monoxide, But Also Tells You The Location Of The Danger, Pre Program Up To 11 Locations In Your Home, Inter Connectable & Can Be Installed & Linked With Up To 18 Compatible Devices, So When One Triggers, All Alarms Sound, 85DD Audible Alarm, Photoelectric Smoke Sensor,Effective At Detecting Slow Smoldering Fires, Battery Backup, Single Test/Silence Button Silences A Non-Threatening Alarm Or Low Battery Warning.