Get from Amazon.com : http://www.amazon.com/gp/product/B002FWGSRK?tag=hawaiianlegac-20<br /><br />Black Box Async RS-232 to RS-485 Interface Bidirectional Converter DB9 Female to Terminal Block<br /><br />Converts RS-232 signals to RS-485 signals <br />Operates at speeds up to 1152 kbps <br />Transmits up to 4000 feet 12192 m <br />Use point-to-point or multipoint
