Black Box RS-232<->RS-422 Converter - serial adapter

The popular RS-232< - >RS-422 Converter provides reliable conversion at speeds up to 64 kbps. You can transmit data up to 4000 feet (1219.2 m) on the RS-422/485 interface - over 4-wire lines in full-duplex operation. In RS-485 mode, select either RTS or DTR to enable the driver. Or set the driver so that it's always enabled.