10 x SITERWELL Hardwired Smoke Detector Interconnected + 9V Backup Battery
If the smoke alarm is in normal working condition, the green LED light is always on and the red LED light flashes every 40 seconds. If low battery there will be a signal alarm, which informs you to change a new battery.
Siterwell Photoelectric Smoke Alarm GS509A Battery Powered 16 Pack
16 pack battery powered smoke alarm new in box ready to go