Question

How does a bidirectional KNX RF device access the bus?

KNX BasicLearnKNX RFMedium
Answer

D — It checks whether the channel is free; if it is occupied it waits until free, then transmits

Correct: bidirectional devices listen first and only send once the channel is free.

Source

KNX Basic Course Documentation — 3.3 — p. 146

All proposed choices (exam context)
  1. A.It transmits immediately regardless of channel state
  2. B.It transmits continuously until an acknowledgement arrives
  3. C.It can only receive and never transmits
  4. D.It checks whether the channel is free; if it is occupied it waits until free, then transmits
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Last updated: 19 May 2026

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