B+B SmartWorx RS-232 Universal Data Splitter

The Universal Serial Data Splitter can be connected so that any two RS-232 devices can be connected to any one RS-232 device. Nine pins are supported: pins 1-8 and 20. Pins 1 and 7 on all three connectors are connected to each other at all times. The other pins must be programmed for proper direction of data flow.
To program the data flow direction requires some knowledge of how your ports are wired. If you are trying to connect two devices to one DCE port (such as a printer) switches 8, 6, and 2 should be on and the other switches off. This OR's the data on pins 3, 5, 6, and 8 together and sends it out the main connector, and allows the data on pins 2, 4, and 20 to flow the other way.