The ATC-863 comes in three versions, the S0, S1 and S2.
ATC-863-S0 = TTL
ATC-863-S1 = RS232
ATC-863-S2 = RS485
The units will only communicate using the protocol that corresponds to the product code. The other connector on the unit does have functionality, but of the same protocol. They can be used for custom applications.
The ATC-863-S1 has a standard RS232 pinout on the DB-9. The terminal block connector has the Tx, Rx and GND for the RS232 connection brought to the terminals for use in a wired application.
The ATC-863-S2 uses the terminal block for RS485. It has the 485+ and 485- brought out to the DB-9 connector for use with a custom cable.