The core element for TP line segment is a TP choke.
In order to power up a TP line segment, its TP choke needs to be connect to a PSU.
In KNX the principle of distributed PSU applies, this means that the same PSU could also be used in order to power up other TP line segments, the
only requirement for a PSU is to make sure that its capacity is not exceeded.
PSU variants: 160 mA, 320 mA, 640 mA, 960 mA, 1280 mA
PL devices use the conventional power cabling as communication medium.
A PL device can only communicate with another PL device if they both belong to the same PL domain.
A PL domain is a collection of PL devices with the same PL domain address.
The PL domain address is a PL device parameter, which can be set with ETS.
A KNX installation can contain several PL domains.
Between a KNX installation containing PL devices and the public grid a band-stop filter shall be installed.
The band-stop filter makes sure that PL telegrams will be not be sent from the KNX installation into the public grid and vice versa.
An RF device can only communicate with another RF device if they both belong to the same RF domain.
An RF domain is a collection of RF devices with the same RF domain address.
The RF domain address is an RF device parameter, which can be set with ETS.
A KNX installation can contain several RF domains.
Couplers contirbute to KNX networks in 3 ways:
- filtering: based on group addresses via filter tables (multicast), and individual addresses (unicast)
- hop count
- LL acknowledgement
the filtering optimizes the traffic on the bus, i.e. couplers make sure that telegrams will only appear there where they are useful.
the filtering is done by couplers only, not by the repeaters.
the destination address of each multicast telegram will be checked. The destination address of a multicast telegram is a group address. If the group address of a telegram is listed in the filter table of the coupler then this telegram will be copied from the primary side to the secondary side or vice versa.
The filter table of a coupler is defined by ETS and depends on the configuration of the ETS project.
the destination address of each unicast telegram will be checked. The destination address of a multicast telegram is an individual address.
whether a unicast telegram is filtered depends on
- where the telegrams comes from
- the individual address of the coupler
IA = 1.1.0
unicast telegram from primary side with destination address = 1.1.55 -> not filtered
unicast telegram from primary side with destination address = 1.0.55 -> filtered
unicast telegram from secondary side with destination address = 1.1.55 -> filtered
unicast telegram from secondary side with destination address = 1.0.55 -> not filtered
the hop count makes sure that multicast telegrams will never travel endlessly through a KNX network even when topological mistakes would be made.
- couplers and repeaters decrement the hop count of multicast telegrams
- multicast telegrams are sent with hop count = 6
- the maximum number of hops between two devices = 6
- couplers and repeaters don't decrement the hop count of unicast and broadcast telegrams
- unicast and broadcast telegrams are sent with hop count = 7
- if sender and destination device are in the same line then LL acknowledgements are sent by the destination device directly, possible repetitions are sent by the sender directly
- if however sender and destination device are not in the same line, then the coupler of the line of the sender will take care of the LL acknowledgements, the coupler of the line of the destination device will take care of possible repetitions