PortServer TS 1/2/4 H MEI halfduplex rs485

J have a problem connecting rs485 device on the port server. The portserver has one port RJ45 8 pins. I successfully connected rs232 device. Which are the port for halfduplex mode for RS485 connection.
For RS232 were 4,5,and 6 for ground. I cant find it for rs485, i used autoloop and hyperterminal to veryfi the correct connections.

Please help

The Quick Start Guide for that product has the RJ45 pinout diagram:


I can connect the TS (4) MEI directly to my device using the RJ45 pin outs (2 wire RS485) but when I remote the unit utilizing RS485 extenders the device stops communicating. The question is how to resolve the signal ground issue while transmitting over the fiber. The model of the fiber transcievers is GE D1300. Any suggestions?