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Chapter 3
Communication Ports
• The number of devices wired should not exceed 32, and total distance should be less than 1219 m (4000 ft) at
100 kbps.
• The Common terminals should be connected to the common wire inside the shield.
• The shield should be connected to earth ground at a single point to avoid loop currents.
• The twisted pair should be terminated at each end of the chain.
The following shows the recommended RS485 wiring.
2
1
Figure 15: Recommended RS485 Wiring
1. RS920W Device
2. Common (Isolated Ground)
6. RS485 Devices (32 Total)
20
3
5
4
120Ω 10nF
3. Negative
5
120Ω 10nF
4. Positive
5. Shield to Earth (Connected At a Single Point)
RUGGEDCOM RS920W
Installation Guide
6
Connecting Multiple RS485 Devices
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