DETEWE OpenCom 130, User Manual

Page: 131 / 204

PBX Networking Connections
129
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 132).
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 confi-
gured. If one PBX is the protocol master for a layer, the other PBX must be the pro-
tocol 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.
Note: In the case of an S
2M
line, it is also possible to deter-
mine for each useful channel which end can administer a
channel (master = internally seized or slave = externally
seized). On S
0
lines this setting is determined by “L3 master”
for both B-channels.
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.
Example: propagation of the L1 clock
PBX 3
PBX 2
Point-to-point
connection
Trunk line
Network
operator
PBX1
M S
M
S
M
M
S
S