Toshiba strata CT Installation & Maintenance Manual page 349

Digital
Telephone
Electronic
Telephone
Standard
Telephone
4773
H
C
Figure 10-17 Primary and Secondary References
Strata CT I&M Manual October 2000
Strata CT
Processor PCB
Synchronisation
Circuit
Time
Switch
Clock
Primary Reference PCB*
PDKU
SS 1
PEKU
RSTU
Secondary Reference PCB*
SS 2
Other RPTU or RBSU
SS 3
Figure 10-17 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 CT digital transmission voice or data path.
The Secondary reference is activated if the Primary reference fails. The Strata CT
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 CT is synchronised to the Line 2 clock
source.
If the path is not synchronised to the Stratum – 1 clock source, calls connected through
that path experience "slipping" in the digital voice or data path (channels).
shows an unsynchronised signal from Line 3. The unsynchronised signal produces a
clicking or popping sound that is heard by the people connected through this path or
causes data errors on data transmissions.
Line 1
Synchronisation
Circuit
Prg *42-1-1
Digital Voice
Path
Line 2
Synchronisation
Circuit
Prg *42-2-2
Digital Voice
Path
Line 3
Synchronisation
Circuit
Prg *41-1[blank]
Prg *42-1[blank]
Digital Voice
Path
Clock not synchronised properly
with Stratum-1 Clock Source
ISDN Interfaces
* Primary/Secondary reference
PCBs are assigned in
Programs 42-1/ 42-2 and
* *
can be an RPTU or RBSU.
Public Switched
Telephone
Network (PSTN)
PRI and BRI
BT or
other provider
PRI and BRI
Clock synchronised properly
with Stratum-1 Clock Source
Other
PRI and BRI
provider
Figure 10-17
Stratum-1
Clock
Source
Other
Clock
Source
10-23