AT&T MERLIN LEGEND Release 4.0 Feature Reference page 85

Feature Reference
Service Profile Identifier
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 to the user 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.
Directory Number
In general, a Directory Number is the telephone number that is dialed to reach a
destination. When an incoming call arrives on a BRI line, the central office
presents the Directory Number as the Called Party Number. Only one call to a
particular Directory Number is accepted at any one time. The Directory Number
is usually a subset of the Service Profile Identifier The DNs for each BRI are still
subsets of the SPIDs. Only the DN for the hunt group are unrelated to the SPIDs.
Clock Synchronization
Clock synchronization is an arrangement in which digital facilities operate from
a common clock. Whenever digital signals are transmitted over a
communications link, the receiving end must be synchronized with the
transmitting end 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 (the clock is synchronized to the external endpoint) or with a 100D
module it can be set to Local Clock Reference Source (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, the first 100D or BRI port in service is the default primary loop
clock source.
Basic Rate Interface (BRI)
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