Felix, you were correct. All that was required was a cross-over of the white and yellow leads in the cable. Thanks.
...Brian

Anyone tried using the UNIT-RS485 module to connect a UHF-RFID tag reader to an RS485 system? The module is typically used to connect TTL serial IO to RS485 but I see no reason that it should not work in reverse, except that it doesn't. I see the serial command on the RS485 side but nothing on the TTL serial IO side.