The USB-485 Communication Interface is a protocol converter used to connect a PC's USB port to the RS-485 input on your Kantech controller KT-1/KT-200/KT-300/KT-400. The maximum bus length is 1,200 m (4,000 ft) when using an Ethernet Grade 3, unshielded, two twisted pair cable (Belden # 1227A recommended).