TEL0038 & TEL0123 RS-232 to RS-485 Converters DFRobot TEL0038 and TEL0123 RS-232 to RS-485 Converters are self-powered, bi-directional adapters designed to convert a full-duplex RS-232 Signal to a half-duplex RS-485 Balanced Differential Signal and extend the communication distance to up to 1.2km.