External powered RS-232 repeater, rail mounted, photoelectric isolation. Features:Communication distance between serial interface RS-232 extended to 1.2 kilometersBalanced electricity transmission with strong ability of anti-interferenceOptical-isolation technology to eliminate grounding loop surge and device damagesIsolated voltage: 2,500Vrms or 500 VDC on a continuous basisRS-232 asynchronic communication standard supportedDirect plug in RS-232..