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Connections PBX Networking
Master/Slave
For an ISDN connection, it is possible to determine which PBX is the protocol master and which the protocol
slave. This relationship can be determined for all three protocol layers independently of one another.
For each protocol layer, the PBX at the other end always has to be suitably configured. If one PBX is the pro-
tocol master for a layer, the other PBX must be the protocol slave for this same layer. Normally all three pro-
tocol layers are configured identically. In the case of a trunk line, the network operator is the protocol master
for all three layers.
L1 Clock
To enable PBXs in the ISDN network to communicate with each other, they must be “clock-aligned”. The L1
protocol master sets the clock for layer 1, and the L1 protocol slave adopts (synchronises to) this clock.
When planning a PBX networking scheme, you must make sure that the L1 clock propagates from a master
via a number of PBXs.
Example: propagation of the L1 clock
If more than one port with the setting L1 Type = “Slave” is configured on anComfort Pro S and the setting
L1 sync possible has been activated, then one of the ports is automatically defined as the L1 clock source.
The Comfort Pro S will automatically switch the clock source to another port configured as an L1 clock
source (if a line fails, for example).
S
Please note: Reciprocal or circular application of the L1 clock is not allowed.
PBX 3
PBX 2
Point-to-point
connection
Trunk line
Network
operator
PBX1
M S
M
S
M
M
S
S