the L1 clock propagates from a master via a number of PBXs.
Network operator
M S
PBX1
M
M S
PBX 3
S
S
PBX 2
M
Trunk line
Point-to-point connection
Example: propagation of the L1 clock
If more than one port with the setting L1 Type = “Slave” is configured on an OpenCom 100 and the setting
L1 sync possible has been activated, then one of the ports is automatically defined as the L1 clock source.
The OpenCom 100 will automatically switch the clock source to another port configured as an L1 clock source
(if a line fails, for example).
Please note: Reciprocal or circu-
lar application of the L1 clock is not allowed.
Example: In the above case you could reverse the L1 slave/master setting for the connection between
PBX 1 and PBX 3. However, if you then activate the setting
L1 sync possible for the port of PBX
1, this may cause parts of the PBX network to stop functioning temporarily.
When applying the L1 clock of trunk lines, you can assume that the public network is “clock-aligned”. So, in the above example, you can connect additional trunk lines to one of the
PBXs.
Types of Point-to-Point Connection
There are different types of connection available for an ISDN point-topoint connection between two PBXs, depending on the distance between them.
Direct Connection
This type of point-to-point connection joins the two systems directly to each other using a crossover twisted-pair cable. An S
0
connection can be used for distances up to
1,000 metres, while an S
2M
connection can span up to 250 meters. Normally one PBX is the protocol master for all three layers, and the other PBX is the protocol slave for all three layers.
PBX 1
L1 master
L2 master
L3 master
Direct connection
PBX 2
L1 slave
L2 slave
L3 slave
■
Use the RJ45 jacks on one of the external S
0
ports for an S
0
con-
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Types of Point-to-Point Connection PBX Networking
