Toshiba Strara CTX Series, Installation And Maintenance Manual, Page: 169 / 290

ISDN Interfaces
5-21
Strata CTX I&M September 2002
Timing and Synchronisation
In the Strata CTX, one PRI or BRI can be programmed to extract the Stratum clock signal. It uses the
signal as the Strata CTX system Primary clock reference. The clock provider should be a reliable
source, such as a network operator. All other PRI or BRI lines connected to the Strata CTX will be
synchronised to the same clock provider. If the PRI or BRI are not synchronised to the same clock
provider, the Strata CTX could experience “slip” problems.
The timing or synchronisation program determines how the Strata CTX digital voice or data
transmission path is synchronised with the far-end digital path. For proper PRI or BRI operation, the
equipment at each end of the line must be synchronised.
The Strata CTX processor time switch is synchronised as the slave to the PRI or BRI line (Line 1 in
Figure 5-20 ).
If a malfunction occurs and Primary reference synchronisation is lost, the Strata CTX automatically
switches modes and synchronises to the Secondary reference, provided that there is another PRI or
BRI installed in the Strata CTX system.
Figure 5-20 Primary and Secondary References
Figure 5-20 shows the Primary reference PCB. The clock signal from Line 1 passes through the
PCB Software Switch (SS
1
) and the synchronisation circuit of the RCTU PCB. The RCTU clock
passes the clock source through the time switch and synchronises the Strata CTX digital
transmission voice or data path.
The Secondary reference is activated if the Primary reference fails. The Strata CTX automatically
switches over to the Secondary reference PCB by opening its synchronisation circuit (SS
1
) and
closing the synchronisation circuit (SS
2
). When this occurs, the digital voice or data path of the
Strata CTX is synchronised to the Line 2 clock source.
5439
PDKU
Primary Reference PCB*
Secondary Reference PCB*
Other RPTU or RBSU
CTX
Digital T
ransmission V
oice
P
ath
Synchronisation
Circuit
Synchronisation
Circuit
Synchronisation
Circuit
Digital Voice
Path
Digital Voice
Path
Digital Voice
Path
CTX
Digital
Telephone
Standard
Telephone
SS1
SS2
SS3
Line 1
Line 2
Line 3
Public Switched
Telephone
Network (PSTN)
PRI or BRI
BT or
other provider
PRI or BRI
Other
PRI or BRI
provider
Stratum-1
Clock
Source
Processor PCB
Clock not synchronised properly
with Stratum-1 Clock Source
Time
Switch
Clock
Synchronisation
Circuit
Clock synchronised properly
with Stratum-1 Clock Source
Other
Clock
Source
RSTU