Red Seal Electrician Practice
Signalling and communicationQuestion 136 of 1506

What does the RS-485 protocol support that RS-422A does not?

  1. Operation on optical fibre
  2. A different voltage level for a 1 and a 0
  3. A speed above 1 Gbps
  4. A multidrop bus with up to 32 addressable nodes
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Correct answer: A multidrop bus with up to 32 addressable nodes

Both use the same differential circuits. RS-422A is point-to-point only.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 14.7: Network Protocols

Practice signalling and communication

Questions last reviewed: 18 October 2026