Master/Slave; L1 Clock - Aastra OpenCom 100 Mounting And Commissioning User Manual

PBX Networking

12.1.2 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 con-
figured. If one PBX is the protocol master for a layer, the other PBX must be the
protocol slave for this same layer. Normally all three protocol layers are configured
identically. In the case of a trunk line, the network operator is the protocol master
for all three layers.

12.1.3 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.
Network
PBX1
operator
M S M
M
S
PBX 2
M
Example: propagation of the L1 clock
Note: All layers of the Q.SIG-IP protocol are symmetrical. The
following are unnecessary: a Master/Slave setting, clock and
synchronisation settings (please refer to Connection via
Q.SIG.IP starting on page 158).
Note: In the case of an S
mine for each useful channel which end can administer a
channel (master = internally seized or slave = externally
seized). On S lines this setting is determined by "L3 master"
0
for both B-channels.
PBX 3
S
S
Trunk line
Point-to-point
connection
line, it is also possible to deter-
2M
Connections
155