Gira 5110 00 Product Documentation page 38

i Expert knowledge:
With KNX TP (TP = Twisted Pair), the bus access of a subscriber is controlled by the
CSMA/CA method (Carrier Sense Multiple Access/Collision Avoidance). This bus access
method avoids telegram collisions. In addition, received telegrams are confirmed by each
addressed TP bus subscriber (telegram confirmation through LinkLayer-Confirm: Ack,
Busy, Nack). This allows transmitters of KNX messages to detect whether potential
receivers have understood the message or whether telegram repetitions are necessary due
to transmission or processing errors.
These security mechanisms are not available within a KNX RF1.R radio domain, due to the
specifications. If there are transmission errors, media couplers, which forward RF
telegrams to the TP side, can repeat telegrams up to three times. Telegrams forwarded on
the RF side are only transmitted once.
Media couplers can perform a telegram confirmation on the TP line for received telegrams.
As described, this is not possible for telegrams received on the RF side.
Order No. 5110 00
Software "Media coupler / repeater"
Parameters
Page 38 of 57