A full-duplex circuit allows both parties to send and receive data simultaneously. D ata C ommunication E quipment, respectively. Software handshaking involves embedding control characters in transmitted data. Hardware handshaking uses voltages on physical wires to control data flow. The RTS and CTS lines of the RS-232 interface are frequently used for this purpose.
Most lab equipment uses hardware handshaking.
This makes RS-422 more immune to noise and interference, and more versatile over longer distances.