21PCs Smoke alarm + 3 Remote

[Interconnected Smoke Alarm] 
The wireless battery-operated interconnected smoke alarms can interconnect with each other, One goes all go wireless interconnected smoke alarms so that they all sound when one is activated, warning you of fire throughout your home and increasing safety, keeping you and your family safe

[Strong compatibility & Multifunctional]
A wireless interconnected smoke alarm fire alarm system can be compatible with other detectors (wireless interconnected Heat detector, wireless interconnected CO detector, Remote controller, Wi-Fi interconnected smoke alarm) wireless-enabled alarms in your home to create a wireless safety network

[Ultra -Large Coverage]
Up to 20~50 compatible interconnected smoke alarms can communicate with each other and alert you when there is a problem across the house even in a different room or on a different floor. Wide Coverage of 20-40m²