PBX Networking
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Example: In the above case you could reverse the L1 slave/master setting for the con-
nection 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.
Point-to-Point Connection Lines
There are different types of lines available for an point-to-point connection between 
two PBXs, depending on the distance between them.
Direct Connection
This type of ISDN 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.
Direct connection
Use the RJ45 jacks on one of the external S
0
 ports for an S
0
 connection between two 
OpenCom 100s. You can use the corresponding pressure terminals for S
0 
ports on 
interface cards.
PBX 1
L1 master
L2 master
L3 master
PBX 2
L1 slave
L2 slave
L3 slave