System interfaces
31
System functions and features as of R4.1
syd-0570/1.2 – R4.1 – 08.2016
CAS on the primary rate interface
CAS (channel-associated signalling) is also used in some countries (e.g. Brazil). With
this method the signalling data is transmitted over the voice channel. The type of sig-
nalling can be selected for each PRI interface ( =dg).
Note:
DSP resources (CAS senders/receivers) are required for CAS. With Mitel 470, DSP resources
for 1 PRI interface are already available on each basic system (on the DSP chip on the call
manager card with fixed function assignment). If more CAS senders/receivers are needed, they
can be assigned on a configurable DSP chip. On an Mitel 430, the DSP resources for CAS
senders/receivers must always be assigned on a configurable DSP chip ( =ym).
2. 1. 2. 1 Clock synchronization
The clock frequency of a communication server is provided (synchronized) by the pub-
lic 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 Mitel 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 net-
work.
Synchronisation on a private fixed network must be carefully planned to ensure there
are no synchronisation loops.
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 con-
figured 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.
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