B&B Electronics 3PCIOU4 - Manual - Manual (Page 50)

DIP Switch / Mode Settings
A-6 Appendix A Document Number 3PCI-0712m
stated when not sending data, allowing other transmitters on the communications line to
transmit without interference.
DIP Switch 2 (RS-422/485 only)
The bottom DIP switch (2) configures the port for half-duplex (two-wire) RS-485
operation or full-duplex (four wire) RS-422/RS-485 operation. Placing the bottom DIP
switch in the RX ON position configures the port for four wire operation. In this mode the
port‘s receiver is continuously enabled, allowing it to receive all data on the
communications line. Since the port‘s transmitter sends data on the other wire pair the
port does not receive its own transmissions.
Placing the bottom DIP switch in the RX position configures the port for two wire
operation. In this mode the port‘s transmitter and receiver are connected to the same
wire pair. The receiver is disabled when its transmitter is sending, preventing the port
from receiving its own data.