HARDWIRED OR WIRELESS INTERCONNECT: These smoke and carbon monoxide detectors can be hardwired or wirelessly connected to up to 12, and when one alarm goes off, all alarms go off, notifying everyone of an emergency. RELIABLE 2-IN-1 PROTECTION:Our alarts combination alarm is equipped with dual sensors, stay safe with this smoke and carbon monoxide detectors in one efficient device,More sensitive and faster detection,enhanced practicality. HUMANIZED VOICE ALERTS: In emergency situations, clearly indicate the type of danger and how to do it through voice alarm, and stay informed of the situation at all times. For example, "Fire! Please leave the building and call 911 immediately" Elderly people and children in the home can react quickly. HARDWIRED ALARM WITH REPLACEABLE BATTERY BACKUP: hardwired smoke and carbon monoxide detector Keeps you and your family safe even during power outages. Detect potential hazards anywhere in the home for total monitoring and security.