Question
How does a unidirectional KNX RF device handle bus access and collisions?
Answer
C — It sends immediately; on a collision it resends, but the 1 % duty cycle makes collisions nearly excluded
Correct: unidirectional devices transmit at once and resend if a collision happens, which is rare thanks to the 1 % duty cycle.
Source
KNX Basic Course Documentation — 3.3 — p. 146
All proposed choices (exam context)
- A.It waits for the channel to be free, then transmits
- B.It never resends, so a collided telegram is simply lost
- C.It sends immediately; on a collision it resends, but the 1 % duty cycle makes collisions nearly excluded✓
- D.It requests a time slot from a central controller first
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