Solution:

(1) Please refer to manual page12. You'd better to OPEN those jumper (JP25, JP26, JP27, and JP28) for Tx control ALWAYS ON with RS-422 mode. Then those other signals (RTS+, RTS-, CTS+, CTS-) are for the handshake. (2) It's depends on your application. [1] Both of the remote computer and your application NEED handshake. Local Remote RTS+ ------ CTS+ RTS - ------ CTS - CTS+ ------ RTS+ CTS - ------ RTS - Besides above connection, you also need to deal with those signal in your program. [2] The remote computer DOESN'T NEED handshake, but your application NEEDS. Local RTS+ --------+ RTS - ---+ | | | CTS - ---+ | CTS+ --------+ [3] Both of the remote computer and your application DON'T NEED handshake. You don't need to do anything about those four signals.