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SYNCHRONIZATION OF DIGITAL FACILITIES
5-9
a duplicated synchronization system, the same DS1 facility provides the primary and secondary
reference for both duplicated halves. Figure 5-5, Duplicated Synchronization Architecture and Cross
Coupling, shows a System 85 or Generic 2 with a duplicated architecture and cross-coupled cables.
PRIMARY
DS1
INTERFACE
SCS 0
MODULE
CLOCK
OR TMS
CLOCK 0
SWITCHING
NETWORK
0
SECONDARY
PORT
CARRIERS
PRIMARY
SECONDARY
DS1
INTERFACE
SCS 1
MODULE
CLOCK
OR TMS
CLOCK 1
SWITCHING
NETWORK
1
Figure 5-5. Duplicated Synchronization Architecture and Cross Coupling
The TN767 is a DS1 circuit pack for a hybrid module; the ANN11 is a DS1 circuit pack for a
traditional module. The standard cable that comes with the TN767 is the H600307. It can be
ordered in eight different lengths, up to 650 feet, by ordering one of eight different group numbers
(groups 1 - 8). See System 85 R2V4 to DEFINITY Communications System Generic 1.1 via ISDN PRI
Access (555-037-233), DEFINITY Communications System Generic 1.1 to 4ESS via ISDN PRI Access
(555-037-234), and DEFINITY Communications System Generic 2.1 to 4ESS via ISDN PRI Access
(555-037-237), for specific cabling and administrative information.
System 85 and Generic 2 Synchronization Software Operation
The synchronization software consists of a series of tasks that monitor several system status
parameters and thus maintain the best synchronization source online. (The online source is the
synchronization reference currently in control. This reference can be either the primary or secondary
reference, or an on-board local oscillator.) Several levels of control are maintained. One level is
controlled by a 1-second software task that uses the system status to keep the best incoming DS1
reference clock online. The other is controlled both by hardware and the 1-second software task to
maintain a healthy SCS on line. If a SCS can receive a suitable reference clock from a DS1, then the
best combination is chosen.
The principal error conditions used to determine if a switch to a different DS1 clock reference is
needed are, in order of importance: