Rs485 Wiring; Figure 32: Conceptual Rs485 Wiring Diagram - RuggedCom RuggedRouter RX1000 Family Installation Manual

4.8 RS485 Wiring

Each RS485 port can communicate to multiple RS485 devices by daisy chaining
devices over a single twisted pair with transmit and receive signals on the same two
wires (half duplex). The following guidelines should be followed to ensure
continuous, reliable communication:
1. To minimize the effects of ambient electrical noise, shielded cabling is
recommended
2. The correct polarity must be observed throughout a single daisy chain
3. The number of devices wired should not exceed 32, and total distance should
be less than 4000 feet (at 100 kbps)
4. The COM terminals should be connected to the common wire inside the
shield.
5. The shield/COM should be connected to earth ground at ONE single point to
avoid loop currents (The RX1000 series RS485 COM terminals are floating,
and therefore not connected to ground).
6. The twisted pair should be terminated at each end of the chain.

Figure 32: Conceptual RS485 wiring diagram

NOTE: If your RX1000 is equipped with four RS232/RS485/RS422 RJ45 ports then
no internal termination is provided.
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RuggedRouter RX1000 Family 33
Communication Ports
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RuggedCom - Rev.122