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Page 14
Wiring Diagram: RS-422
Figure 2.14. RS‐232/485 RF Modem in an RS‐485 (4‐wire) environment
RS-485/422 Connection Guidelines
The RS-485/422 protocol provides a solution for wired communications that can tolerate high
noise and push signals over long cable lengths. RS-485/422 signals can communicate as far as
4000 feet (1200 m). RS-232 signals are suitable for cable distances up to 100 feet (30.5 m).
RS-485 offers multi-drop capability in which up to 32 nodes can be connected. The RS-422
protocol is used for point-to-point communications.
Suggestions for integrating the RS-232/485 Modem with the RS-485/422 protocol:
1.
2.
3.
4.
Figure 2.15. Male DB‐9 to RJ‐45 Adapter (yellow)
Figure 2.16. Female DB‐9 to RJ‐45 Adapter (green)
When using Ethernet twisted pair cabling: Select wires so that T+ and T- are connected to
each wire in a twisted pair. Likewise, select wires so that R+ and R- are connected to a
twisted pair. (For example, tie the green and white/green wires to T+ and T-.)
For straight-through Ethernet cable (not cross-over cable) – The following wiring pattern
works well: Pin3 to T+, Pin4 to R+, Pin5 to R-, Pin6 to T-
Note that the connecting cable only requires 4 wires (even though there are 8 wires).
When using phone cabling (RJ-11) – Pin2 in the cable maps to Pin3 on opposite end of cable
and Pin1 maps to Pin4 respectively.
RS‐232/485 RF Modem Product Manual – MAN0782‐02
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