Single-mode communication distance up to 20 km. ^^ Support RS-232, RS-422 and RS-485 asynchronous communication protocols ^^ It supports asynchronous RS-232, RS-485, RS-422 communication interface, which is the best choice for connecting remote terminal unit (RTU) to host computer (HOST) or distributed data acquisition system (SCADA) controller. ^^ Optional SC, FC, ST interfaces are available. This is ST interface. If you need other interface types, please contact our customer service. ^^ Supports 2-wire (half-duplex) and 4-wire (full-duplex) RS-485 operation