Use coaxial lines to transmiss the real time digital, distance up to 220m. ^^ Fast and easy to install, save the cables, the installation cost and time. ^^ Convenient to use. Passive device, no power required. ^^ Built in, safety in use. ^^ The traditional coaxial line analog camera system is upgraded to the network HD camera, both of which can be replaced directly. ^^ ^^ ^^ ^^ ^^