B&B Electronics offers a wide range of converters including the DIN rail mountable Model 485DRCI.  This unit optically isolates and converts unbalanced, full or half-duplex RS-232 signals to optically isolated, balanced, full or half-duplex RS-422 or RS-485 signals. It also includes surge suppression on the RS-422/485 lines and features Send Data Control circuitry that ensures no software control of handshake lines is required in RS-485 mode.