AMT/PTD/PBX/0058/4/6/EN Installation and Maintenance Manual - Aastra 5000
Page 100 01/2011 Description et caractéristiques d’un PBX
3.8.4 Synchronisation chain (Plate 9.1)
The synchronisation function ensures that an iPBX or an iPBX network is synchronised on
a public digital network, and provides the multi-frame synchronisation required for DECT
base stations.
3.8.4.1 Synchronisation of an isolated or master iPBX in a multi-site network
The UCV CPU card contains a time base used to synchronise the iPBX on an external
reference clock. The latter can be chosen from 6 clocks extracted from the digital
connections of an RTCP network (T0 or T2) through LT2, LD4, LD4N and LD4X
synchronising expansion cards.
For an AXS, there are 4 reference external clocks on the UCV-S CPU card, 3 of which are
taken from expansion cards and one from the ISDN accesses integrated in the EXT1S
card.
These LT2, LD4, LD4N and LD4X cards must be fitted in slots 0 to 5 in the main cabinet of
the AXL and AXD iPBXs (slots 0 to 2 for AXS). All the EXT1-S ISDN accesses are
synchronising.
The first active digital network card synchronises the system. It maintains this as long as
its clock is valid, and in the absence of higher priority clocks. Otherwise, a new clock is
sought.
The time base generates and distributes two synchronisation signals to the cards in the
cabinet, and possibly to the other iPBXs in a multisite configuration:
• An HBIT synchronisation clock
• An HDECT synchronisation clock derived from the bit synchronisation
The external reference clocks can belong to 2 priority classes (high priority and low
priority); the clock provided by the card located in slot 0 is high priority and the other 5
clocks are low priority.
The reference clock, selected according to its priority class, can be used to reset the
internal oscillator present on the main card.
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