660MBX-Optical-Smoke-Alarm-Mains-Powered-with-Battery-Backup-BRK-660MBX-p-The-BRK-reg-660MBX-Optical-Smoke-Alarm-is-mains-powered-with-a-9V-alkaline-battery-backup-that-will-provide-power-in-the-event-of-a-mains-failure-Thermally-enhanced-optical-technology-reduces-nuisance-alarms-This-alarm-features-a-test-&-alarm-pause-button-&-will-also-notify-you-in-the-event-of-a-low-battery-LED-operating-indicators-&-an-alarm-source-indicator-It-can-be-connected-with-up-to-12-compatible-s