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2.1 Introduction
Each Basic Rate Interface on the CBUQBR operates as a TE. This
provides 64kbit/s 'B' channels for the consumption of other user cards in
the Shelf System. The CBUQBR operates as the sole provider of 'B'-
channels within the Shelf.
The other application cards are completely responsible for the provision
of telephone numbers, CLID's, dial commands, timers, call retry etc. -
the CBUQBR has no facility for storing these facilities.
2.2 ISDN Interfaces
Four Basic Rate ISDN 'S' interfaces are provided conforming to the I.420
standard.
Line termination resistors can be selected (in or out) by jumpers on the
rear interface card. Sometimes termination is required with long cable
lengths to the ISDN termination point.
2.3 Clocking
The clock for the system is derived from the network. One interface acts
as a clock master and generates clock and frame sync for the system.
The remainder the CBUQBR provides elastic buffering to remove any
clock phase jitter.
80-14004000-01
2
Operation
Operation
2–1
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