Total isolation between RS-232 based systems and RS-422 is provided by Telebyte's Model 265 RS-232 to RS-422 Optically Isolated Interface Converter. Unique circuitry allows the RS-422 port to withstand surges exceeding 10 kilovolts. A switch is included to reverse Pins 2 and 3 of the RS-232 connector to accommodate DTE or DCE ports. Data flow is displayed on TD and RD LED indicators. The RS-232 input is a DB25 male connector. The RS-422 interface is a five position terminal strip where one of the terminals is an earth ground connection, used when the environment can produce surges on the two twisted pairs of the RS-422 port. Since the RS-422 circuitry is optically isolated a separate power supply (a wall mounted transformer) is included for the RS-422 port. The power for the RS-232 interface is derived from TD or any one of the control pins of the interface, 4 (RTS), 5 (CTS), 6 (DSR), 8 (DCD), or 20 (DTR). Full duplex transmission is provided up to 19.2 KBPS over a distance of 2 miles.