Please be more specific. There are some RS 485 repeaters, but choice of them depends on what you want to do. Protocols (like Modbus) needs more specifications than transmission standards (like RS 485), where such "standards" still necessify explanations.
I was looking for Modbus Splitter recently also.
I manage to get from ProLinx as per:
ftp://ftp.prolinxgateways.com/ProLinx/Datasheets/4102_PE.pdf
OR http://www.prolinxgateways.com/downloads.html (search for 4102-MBS3-MBM)
The ProLinx 4102 hardware is a generic 4-port serial device that will convert between various protocols or act as an expander depending on firmware loaded. To make it act as a ¡§1 port to 3 port¡¨ expander, you will need to order part number 4102-MBS3-MBM to ensure the correct firmware is loaded. The ProLinx 4102 hardware is a generic 4-port serial device that will convert between various protocols or act as an expander depending on firmware loaded. To make it act as a ¡§1 port to 3 port¡¨ expander, you will need to order part number 4102-MBS3-MBM to ensure the correct firmware is loaded.