104
PBX Networking
PBX Networking
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 mas-
ter via a number of PBXs.
Example: propagation of the L1 clock
If more than one port with the set-
ting
L1 Type
= “Slave” is configured
on an OpenCom 510 and the setting
L1 sync possible
has been activated,
then one of the ports is automati-
cally defined as the L1 clock source.
The OpenCom 510 will automatically
switch the clock source to another
port configured as an L1 clock source
(if a line fails, for example).
LED 3 (top right) of an interface card
will light up if one of the interfaces
on the card has been selected as a
clock source. If an S
2M
interface of
the type MS+S2M1-1 is installed, it
will be selected as the preferred
clock source.
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 tempo-
rarily.
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 ad-
ditional trunk lines to one of the
PBXs.
Types of Point-to-Point
Connection
There are different types of connec-
tion available for an ISDN point-to-
point connection between two PBXs,
depending on the distance between
them.
Direct Connection
This type of point-to-point connec-
tion 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 3
PBX 2
Point-to-point
connection
Trunk line
Network
operator
PBX1
M
S
M
S
M
M
S
S
Summary of Contents for OpenCom 510
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