Funlux 720p Smart Security Camera System, 8 HD Wireless IP Cameras with Night Vision, Smartphone Viewing, White Funlux Camera ZM-W0004-8 8xHD WiFi Smart Security Camera Night Vision 720p Brown Box The plug is for the power source because the camera doesn't run on batteries and you need a router so it can be on a network Each camera must be paired to there respective router in each home. ie Home A-3 camers paired to that particular router. Home B- Those camera cameras must be paired with that respective router.