For the 983EN module, each channel includes circuitry for both input and output functions that requires you to do two things.
1. Wire to the terminal connection your input or output circuit.
2. Issue the appropriate command: For an input circuit, issue a READ command. The address reference for a READ command is 1xxxx.
For an output circuit, issue a WRITE command, The address reference for a WRITE command is 0xxxx.
The really nice feature is that for output circuit connections, you can issue a write command first to open or close the contact, then issue a read command immediately after that to confirm that the output contact did what it was supposed to do. This is called a "read back" feature and only needs one terminal connection to do it.