Aastra 400 Series - Clock Synchronization; Digital Down-Circuit Connection with QSIG

System interfaces
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System functions and features as of R3.0
syd-0367/1.3 – R3.0 – 03.2013
2. 1. 2. 1 Clock synchronization
The clock frequency of a communication server is provided (synchronized) by the
public network via the basic accesses BRI-T and the primary rate accesses PRI.
Should synchronization by the public network fail (due, for example, to exchange
line interruptions), the communication server will use its own clock. This frequency
deviates at most by 5 ppm from the nominal value, which ensures that the
Aastra DECT system also remains available.
In a private leased-line network, PINXs that are synchronized by the public network
pass on the clock reference to PINXs that are not connected directly to the public
network.
Synchronization in the private fixed network has to be carefully planned to ensure
there are no synchronization loops (see "PISN/QSIG networking" System Manual,
"Synchronization" Chapter).
All the private leased-line network connections and public exchange line circuits
are automatically in a shared clock reference table when the communication server
is configured for the first time.
If a communication server is not networked in a PISN, the clock reference table can
be left as it is; only the initial reference may have to be assigned differently.
2. 1. 2. 2 Digital down-circuit connection with QSIG
If a down-circuit communication server is connected with an up-circuit communi-
cation server via digital lines (BRI-T, PRI), all the features as per QSIG are available
providing the up-circuit communication server supports the QSIG protocol.
The down-circuit communication server is configured in accordance with the rules
for networked systems.
The up-circuit communication server has a connection to the public network. It can
also be an Aastra 400 system or a third-party product, provided it supports the
QSIG protocol.
As a rule the down-circuit communication server is connected with the up-circuit
communication server via its own fixed lines. The interfaces can be basic rate inter-
faces (BRI-T) or primary rate interfaces (PRI). Connections on an S
external-type in-
terface are also possible instead of connections on a BRI-T interface, providing at
least one BRI-T interface is available for synchronization via the ISDN network.