Synchronization; Clock Propagation Diagram - ASCOM Ascotel 2025 System Manual

6.1.7

Synchronization

A PBX's clock frequency is predefined (synchronized) by the public network via
basic accesses T and primary rate accesses T2.
If the synchronization provided by the public network fails (due, for instance, to
interrupted trunk lines), the PBX will use its own clock frequency.
In the private leased-line network, systems synchronized by the public network
pass on the clock reference to systems that are not directly connected to the pub-
lic network.
6.1.7.1

Clock Propagation Diagram

Synchronization in a private leased-line network has to be carefully planned to
ensure that synchronization loops never occur. A synchronization loop occurs
whenever two systems synchronize each other.
The best solution is to sketch out a clock propagation diagram based on the fol-
lowing pattern:
1. Enter the network systems.
2. Draw the connecting lines between the systems.
3. Determine where the clock is forwarded from and to:
– Add direction arrows to the connecting lines. Make sure no loops are cre-
ated.
– To check the arrangement, follow the path in the direction of the arrows:
If you never encounter the same system twice on the same path, you can
assume that there are no loops.
4. Define network interfaces (T2, T or S external).
5. For each system configure the network interfaces of all the trunk lines with an
incoming arrow in the clock reference table. One of these will then be chosen
as the original reference.
HBT_20321104_03/B0_en
ascom Ascotel 2025/2045/2065
Planning a Private Network 3.97