Atlona RS-232 Extender over Twisted Pair Cat5/6 up to 825ft. Model: AT- RS232SRS. Atlona AT-RS232SRS RS-232 Extender(Receiver/Transmitter) Kit over Twisted Pair Cat5/6 up to 825ft. The AT-RS232SRS consists out of 2 x boxes; one takes RS232 9-pin connector and converts it to Twisted Pair (Cat5/6).
eBay