B&B Electronics 4WSD9R - Datasheet - Manual (Page 3)

4WSD9R0712-3/4
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Table 5: Switch settings for
RS-422 4-wire full-duplex
Switch # Position
1 RS-422
2 Echo On
3 4-wire
4 4-wire
Figure 2: RS-485 4-wire full-duplex diagram
RS-422 4-Wire Full-Duplex:
This communications mode is typically used for point-to-point communications over long
distances with better noise immunity than RS-232. Another common use would be as the
master in a master/slave configuration. The RS-422 driver and receiver are always
enabled to allow full-duplex communications. In order to do this there must be a pair of
wires dedicated to the driver, a pair dedicated to the receiver, and a ground reference
wire
i
for a total of 5 lines to operate properly. To set up for this mode, put switch 1 in the
RS-422 position, switch 2 in the Echo On position, and switches 3 and 4 in the 4-wire
position as shown in Table 5.
Figure 3: RS-422 4-wire full-duplex diagram
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i
If you are concerned about creating ground loops by connecting grounds of units together, please check into
B&B Electronics’ line of optically isolated RS-232 to RS-422/485 units such as the 485OT9L.
9-pin M/F cable
9-pin M/F cable