The STP-100 is also equipped with two 4-pin RJ11 RS-485 interface connectors that will allow for multiple boards to be chained together in a network.  The RS-485 connectors allow for full duplex multi-drop communication with a host computer when used in conjunction with the PP232-485f.
 
 

An example for connecting multiple boards with the PP232-485f

Features:

• Converts RS-232 level signals to RS-485 level signals
• Use two to extend RS-232 cable runs to 2000 ft.
• Operates on 7 - 15V DC