MERLIN LEGEND Communications System Release 5.0
Feature Reference
555-650-110
Issue 1
June 1997
Features
Page 86
Basic Rate Interface (BRI)
Service Profile (SP)
3
A
Service Profile (SP)
defines the interface on a BRI line between the central
office and an ISDN terminal. It specifies the parameters and their values
necessary to provide services to the terminal.
Service Profile Identifier (SPID)
3
A
Service Profile Identifier (SPID)
is a unique identifier used by the central office
to associate an ISDN terminal with a Service Profile. It is provided by the central
office at subscription time. The system manager must program the SPID for each
BRI line to bring the BRI line into service (activate). If dial tone is received, then
the correct SPID has been programmed.
Clock Synchronization
3
Clock synchronization is an arrangement where digital facilities operate from a
common clock. Whenever digital signals are transmitted over a communications
path, the receiving end must be synchronized with the transmitting end in order to
receive the digital signals without errors.
The system synchronizes itself by extracting the timing signal from the incoming
digital stream. If the system has one 100D module, that module provides its own
primary synchronization. If the system has at least one 800 NI-BRI module, more
than one 100D module, or a combination of 100D modules and 800 NI-BRI
modules, then one of the connections provides primary clock synchronization for
all 800 NI-BRI and 100D module ports and for the system’s
time-division
multiplexing (TDM)
bus. The primary clock synchronization source must be
identified during system programming. The factory setting is the first 100D module
in service or the first port in service on the first 800 NI-BRI module in the carrier.
This can be changed through system programming.
In the event of a maintenance failure of primary synchronization, backup
synchronization can be provided by secondary and tertiary clock synchronization.
In addition, the source of synchronization is factory-set to Loop Clock Reference
Source, so that the clock is synchronized to the outside source. With a 100D
module, it can be set to Local Clock Reference Source so that the clock is
free-running. However, this is not recommended for most permanent installations
and systems with Primary Rate Interface (PRI). This setting must be made for the
primary, secondary, and tertiary synchronization sources.
On a frigid start (System Erase), the first 100D or BRI port in service is the default
primary loop clock source.
The following lists the options for primary, secondary, and tertiary clock
synchronization sources in order of preference:
1.
The clock sources on BRI ports with DSLs in service. If at all possible, all
three clock sources should be on the same 800 NI-BRI module.
2.
The loop clock source on any 100D module.
