xmartO [Audio Video & Color Night Vision]  8CH 960p HD Expandable Wireless Security Camera System with 4x 960p HD WiFi Night Color Outdoor IP Cameras, Dream Liner WiFi Relay, Built-in Router, No HDD With audio support, the xmartO camera system lets you add microphone to each camera; letting you see, hear and record AV (audio & video). Dream Liner WiFi Relay Tech - The xmartO Dream Liner technology uses cameras in middle as repeaters. That way, further cameras connect to closer cameras 1st, and then to the NVR as a group. This theoretically doubles/ triples the current WiFi distance. NVR built-in Router  With built-in router, the NVR ensures reliable and stable WiFi connections with cameras. It does not use your home router bandwidth, reserves your home WiFi bandwidth for your TVs, tablets & phones. The system works even without any Internet connection. Easy setup, Plug & Play  NVR and cameras AUTO-PAIR, you only need to plug them to power and hook up to a monitor/TV, you see cameras video immediately. Supports adding 4 more cameras. Mobile Live View & Playback  Free mobile app and cloud technology enable you to view the cameras on your phone/ pad in 3 simple steps. You can also remote playback history videos in the hard drive from your phone/pad.